xspeed / includes / class-cache.php

class-cache.php in xSpeed Cache: AI-Powered Performance Hub with MCP, Caching & CDN 1.1.8, at includes/class-cache.php

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1	<?php
2	/**
3	* Page cache engine.
4	*
5	* @package XSpeed
6	*/
7
8	namespace XSpeed;
9
10	defined( 'ABSPATH' ) \|\| exit;
11
12	class Cache {
13
14	/**
15	* Output-buffer nesting level at which we opened our cache buffer, so
16	* `close_buffer()` can flush ONLY our buffer and never disturb a buffer
17	* another plugin pushed on top of (or below) ours.
18	*
19	* @var int\|null
20	*/
21	private static $buffer_level = null;
22
23	/**
24	* The `X-XSpeed-Cache` value decided for this request, and — when the
25	* decision was BYPASS — the slug of the gate that made it.
26	*
27	* Recorded as well as sent so unit tests (CLI SAPI, where header() is a
28	* no-op and headers_sent() is meaningless) can assert on the decision.
29	*
30	* @var string
31	*/
32	private static $status_header = '';
33	private static $bypass_reason = '';
34
35	/**
36	* Cache key whose write was deferred to shutdown because a render-time
37	* translation plugin's buffer wraps ours. Null on every ordinary request.
38	*
39	* @var string\|null
40	*/
41	private static $deferred_key = null;
42
43	/**
44	* Translated page HTML captured by the outer buffer, for the deferred
45	* write. Only populated when a translation plugin is active.
46	*
47	* @var string
48	*/
49	private static $translated_output = '';
50
51	/**
52	* Did finalize_buffer() run to completion on this request?
53	*
54	* The deferred translated write runs as a PHP shutdown function, which
55	* fires after a `wp_die()` or a bare `exit()` exactly as it does after a
56	* clean render. Only finalize_buffer() sets this, and only at the point
57	* where it has the full buffer in hand — so an aborted render leaves it
58	* false and the writer declines rather than caching a truncated page
59	* under the real key.
60	*
61	* @var bool
62	*/
63	private static $render_completed = false;
64
65	public function __construct() {
66	/**
67	* When the page-cache output buffer opens.
68	*
69	* Filterable because buffer ORDER decides what gets cached. PHP's
70	* output buffers are LIFO: the last one opened is innermost, and its
71	* callback runs first. A render-time translation plugin that opens
72	* an outer buffer therefore translates AFTER we have already captured
73	* and cached the raw HTML — see translation_buffer_compat().
74	*
75	* @param string $hook Hook to open the buffer on.
76	* @param int $priority Priority for that hook.
77	*/
78	$hook = (string) apply_filters( 'xspeed_cache_buffer_hook', 'template_redirect' );
79	$priority = (int) apply_filters( 'xspeed_cache_buffer_priority', 0 );
80	add_action( $hook, array( $this, 'maybe_start_cache' ), $priority );
81
82	// When a render-time translation plugin is present, open one extra
83	// buffer OUTSIDE its own so we can capture post-translation HTML.
84	// TranslatePress opens on `init` priority 0, so we take a negative
85	// priority to land outside it. This buffer only collects bytes for
86	// the deferred cache write — it never modifies the response.
87	add_action(
88	'init',
89	static function () {
90	if ( ! self::translation_plugin_active() ) {
91	return;
92	}
93	// `init` fires on EVERY request type, and
94	// translation_plugin_active() is a class_exists() check that
95	// is true site-wide — so without this guard the buffer opened
96	// on REST, admin-ajax, cron and WP-CLI too. None of those
97	// reach template_redirect, so $deferred_key stays null and
98	// the collected bytes are never released: a long-running
99	// WP-CLI command copied every byte of its output into a
100	// string that grew for the life of the process.
101	if ( is_admin()
102	\|\| wp_doing_ajax()
103	\|\| wp_doing_cron()
104	\|\| ( defined( 'REST_REQUEST' ) && REST_REQUEST )
105	\|\| ( defined( 'WP_CLI' ) && WP_CLI )
106	\|\| ( defined( 'XMLRPC_REQUEST' ) && XMLRPC_REQUEST ) ) {
107	return;
108	}
109	ob_start(
110	static function ( $chunk ) {
111	self::$translated_output .= $chunk;
112	return $chunk;
113	}
114	);
115	},
116	(int) apply_filters( 'xspeed_translation_outer_buffer_priority', -100 )
117	);
118
119	// Events that should invalidate cached output. Beyond posts/comments,
120	// this covers user and term changes — the REST cache can serve
121	// /wp/v2/users, /wp/v2/categories, /wp/v2/tags, and these also affect
122	// rendered author bylines / term-archive pages. Without them, an edit
123	// left the matching endpoint (and archives) stale for the full TTL.
124	// (FBS-82408)
125	$invalidate_hooks = array(
126	'save_post', 'deleted_post', 'trashed_post',
127	'comment_post', 'wp_set_comment_status',
128	'switch_theme', 'activated_plugin', 'deactivated_plugin',
129	// Users → /wp/v2/users + author archives.
130	'profile_update', 'user_register', 'deleted_user',
131	// Terms → /wp/v2/{taxonomy} + term archives.
132	'created_term', 'edited_term', 'delete_term',
133	);
134	foreach ( $invalidate_hooks as $hook ) {
135	add_action( $hook, array( __CLASS__, 'purge_all' ) );
136	add_action( $hook, array( 'XSpeed\\Minifier', 'purge_minified' ) );
137	}
138
139	add_action( 'update_option_xspeed_options', array( __CLASS__, 'on_settings_change' ), 10, 2 );
140
141	// …and the same for every PER-MODULE option. The handler above only
142	// ever watched the legacy `xspeed_options` blob, but every module has
143	// since migrated to its own `xspeed_module_<slug>` option and no hook
144	// followed — so changing Minify HTML, Lazy Load, Remove Query Strings
145	// etc. left the cached HTML untouched until the TTL expired (24h by
146	// default) and the feature read as broken. (#205)
147	//
148	// One central listener rather than a hook per module: it covers Pro
149	// modules with no cross-repo change, and a new module can't forget to
150	// wire it up.
151	add_action( 'updated_option', array( __CLASS__, 'on_module_settings_change' ), 10, 1 );
152	// `added_option` matters as much as `updated_option`: on a fresh install
153	// a module's option doesn't exist yet, so the FIRST save of every panel
154	// goes through add_option() and would otherwise skip the purge — the
155	// original bug surviving one save per module. `deleted_option` covers a
156	// reset-to-defaults, which changes rendered HTML just as much. (#205)
157	add_action( 'added_option', array( __CLASS__, 'on_module_settings_change' ), 10, 1 );
158	add_action( 'deleted_option', array( __CLASS__, 'on_module_settings_change' ), 10, 1 );
159
160	add_action( 'admin_bar_menu', array( $this, 'admin_bar_purge' ), 100 );
161	add_action( 'admin_post_xspeed_purge', array( $this, 'handle_admin_bar_purge' ) );
162	}
163
164	public static function on_settings_change( $old, $new ) {
165	// gzip_enabled moved to xspeed_module_gzip — GzipModule owns the
166	// .htaccess flip via its own update_option_xspeed_module_gzip hook.
167	// Same migration is planned for cache_expiry + excluded_urls
168	// (Cache module). Keep this handler around for whatever still
169	// lives in the legacy blob (cache_enabled is special and goes
170	// through Cache::toggle anyway).
171
172	// Any settings change — purge caches so changes take effect.
173	self::purge_all( 'settings change' );
174	Minifier::purge_minified();
175	}
176
177	/**
178	* Modules whose settings cannot change rendered HTML, so a write to them
179	* doesn't warrant throwing away the page cache.
180	*
181	* The safe default is to purge: a module is listed here only when it is
182	* clearly incapable of altering front-end output (diagnostics, the MCP
183	* server, licensing/telemetry surfaces). When in doubt, leave it off the
184	* list — a needless purge costs a re-render, a missed one makes the
185	* feature look broken. (#205)
186	*
187	* @return string[] Module slugs.
188	*/
189	public static function non_rendering_modules(): array {
190	return (array) apply_filters(
191	'xspeed_non_rendering_modules',
192	array(
193	'mcp', // AI endpoint — no front-end output.
194	'health', // diagnostics only.
195	'support', // support snapshot.
196	'score', // PageSpeed/GTmetrix runner.
197	'migration', // one-shot importer.
198	'settings', // import/export surface.
199	'cache-coverage', // read-only reporting.
200	'ai-privacy', // consent flags for AI surfaces.
201	'database', // DB cleanup schedule — no HTML impact.
202	// Pro slugs — listed by name rather than by asking Pro, so
203	// Free stays unaware of it. A Pro module absent here simply
204	// purges, which is the safe default.
205	'license',
206	'pro_status',
207	'analytics',
208	'performance-health',
209	'recommendations',
210	'ai-provider',
211	'migration-pro',
212	)
213	);
214	}
215
216	/**
217	* Purge when ANY module's settings option is written. (#205)
218	*
219	* Bound to `updated_option`, `added_option` and `deleted_option` — all three
220	* fire for every option on the site, so the prefix test comes first and is
221	* the cheap path for the ~99% of writes that aren't ours. All three pass the
222	* option name first, which is why this can't hook purge_all() directly:
223	* that takes $cause first, so every purge would be filed under a cause
224	* literally named "xspeed_module_minify".
225	*
226	* @param string $option Option name that was just written or removed.
227	*/
228	public static function on_module_settings_change( $option ): void {
229	$option = (string) $option;
230	$prefix = Settings_Manager::OPTION_PREFIX;
231	if ( 0 !== strpos( $option, $prefix ) ) {
232	return;
233	}
234
235	$slug = substr( $option, strlen( $prefix ) );
236	if ( '' === $slug \|\| in_array( $slug, self::non_rendering_modules(), true ) ) {
237	return;
238	}
239
240	// Guard against re-entry: purge_all() and purge_minified() can write
241	// options of their own (stats, timestamps), and a nested purge would
242	// both waste work and risk recursing through this same hook.
243	static $purging = false;
244	if ( $purging ) {
245	return;
246	}
247	$purging = true;
248
249	self::purge_all( 'settings change' );
250	Minifier::purge_minified();
251
252	$purging = false;
253	}
254
255	/**
256	* Stamp the request's cache decision on the response.
257	*
258	* `X-XSpeed-Cache` was only ever written on the serve-from-cache paths,
259	* so a miss and a deliberate bypass both came back with no header at all
260	* — indistinguishable from a `curl -I`, the first thing anyone reaches
261	* for when a site "isn't caching" (issue #10). The reason slug rides
262	* along on `X-XSpeed-Reason`, but only under WP_DEBUG so production
263	* responses stay clean. Slugs are fixed per gate — never the matched
264	* pattern, cookie or user-agent, which would echo request input back.
265	*
266	* @param string $value HIT (php) \| MISS \| BYPASS.
267	* @param string $reason Fixed slug naming the gate, for BYPASS only.
268	*/
269	private static function mark( string $value, string $reason = '' ): void {
270	self::$status_header = $value;
271	self::$bypass_reason = $reason;
272
273	if ( headers_sent() ) {
274	return;
275	}
276	header( 'X-XSpeed-Cache: ' . $value );
277	if ( '' !== $reason && defined( 'WP_DEBUG' ) && WP_DEBUG ) {
278	header( 'X-XSpeed-Reason: ' . $reason );
279	}
280	}
281
282	/** Record a bypass gate and answer "don't cache" in one statement. */
283	private static function bypass( string $reason ): bool {
284	self::mark( 'BYPASS', $reason );
285	return false;
286	}
287
288	/** The X-XSpeed-Cache value decided for this request ('' if none yet). */
289	public static function status_header(): string {
290	return self::$status_header;
291	}
292
293	/** The bypass gate slug for this request ('' unless BYPASS). */
294	public static function bypass_reason(): string {
295	return self::$bypass_reason;
296	}
297
298	/**
299	* Bypass gates that describe THE VISITOR rather than THIS REQUEST.
300	*
301	* Only these may be recorded in the bypass cookie. A visitor-scoped
302	* verdict stays true for the visitor's next request — they are still
303	* logged in, still hold a cart cookie — so the web server can act on
304	* it without booting PHP.
305	*
306	* Every other gate describes the request in front of us: its method,
307	* its URL, its query string, the client's user agent. Persisting one
308	* of those pins a visitor to the uncached path over a property that
309	* was never theirs to begin with. (#218)
310	*/
311	private const VISITOR_SCOPED_BYPASS = array( 'logged-in', 'excluded-cookie' );
312
313	/**
314	* Whether $reason describes the visitor (persist it) or merely this
315	* request (don't).
316	*
317	* Split out as a pure function because it is the whole decision behind
318	* the bypass cookie, and the cookie write itself (setcookie()) can't be
319	* asserted in a unit test.
320	*/
321	public static function bypass_is_visitor_scoped( string $reason ): bool {
322	return in_array( $reason, self::VISITOR_SCOPED_BYPASS, true );
323	}
324
325	public function maybe_start_cache() {
326	if ( ! self::should_cache() ) {
327	// PHP has just evaluated the FULL exclusion rule list — including
328	// the `~regex` patterns the server config can't express — and
329	// decided this response must not be served from cache. Record that
330	// verdict in the conventional bypass cookie so the web server can
331	// enforce it on subsequent requests without starting PHP.
332	//
333	// This is what stops most settings changes from needing an nginx
334	// reload: the config tests one fixed cookie name forever, and the
335	// rule list behind it can change freely.
336	//
337	// But ONLY when the verdict is about the visitor. A request-shape
338	// gate — `non-get` above all — says nothing about who is asking,
339	// and persisting it pinned that visitor to the uncached path for
340	// the rest of their session: one search-form POST, one comment,
341	// one `curl -I` from an uptime monitor, and every later GET
342	// bypassed. It could not self-heal either, because the bypass
343	// cookie is itself in excluded_cookies, so the next GET bypassed
344	// with `excluded-cookie` and landed right back here, where
345	// sync_bypass_cookie()'s no-change short-circuit left the cookie
346	// exactly where it was. (#218)
347	if ( self::bypass_is_visitor_scoped( self::bypass_reason() ) ) {
348	self::sync_bypass_cookie( true );
349	}
350	return;
351	}
352
353	// Cacheable: clear any stale bypass cookie, or a visitor who once
354	// had a cart would keep skipping the fast path long after checkout.
355	self::sync_bypass_cookie( false );
356
357	$key = self::cache_key();
358	$file = self::cache_file_for( $key );
359
360	if ( file_exists( $file ) && ! self::is_expired( $file ) ) {
361	Hit_Counter::record_hit();
362	// Emit the HIT marker on THIS path too. The drop-in
363	// (advanced-cache.php) sends "HIT (php)" and the nginx static
364	// rewrite sends "HIT (nginx)", but this template_redirect
365	// serve path — the one that runs when the drop-in isn't loaded
366	// (e.g. WP_CACHE not true) — previously streamed the cached
367	// file with NO marker, so a genuine HIT looked like a MISS in
368	// the response headers. Same header + value as the drop-in.
369	self::mark( 'HIT (php)' );
370	// Replay stored response bits so the HIT matches the original:
371	// a non-HTML Content-Type (cached feeds, sitemaps) and a non-200
372	// status (a cached 404 must serve 404, not 200). No-op for
373	// ordinary pages, which write no .meta.
374	$meta = self::read_meta( $key );
375	if ( ! headers_sent() ) {
376	if ( ! empty( $meta['status'] ) && function_exists( 'http_response_code' ) ) {
377	http_response_code( (int) $meta['status'] );
378	}
379	if ( ! empty( $meta['content_type'] ) && is_string( $meta['content_type'] ) ) {
380	header( 'Content-Type: ' . $meta['content_type'] );
381	}
382	// Conditional GET: emit Last-Modified + ETag and answer a
383	// matching If-Modified-Since / If-None-Match with 304 so
384	// aggregators (and browsers) skip re-downloading an unchanged
385	// cached response — the bandwidth win feeds are about.
386	// (FBS-82407 #5)
387	if ( self::serve_not_modified( $file ) ) {
388	exit; // 304 sent, no body.
389	}
390	}
391	// Serve the precompressed Brotli sibling when the client accepts
392	// it (an add-on, the Pro Brotli module, wrote <file>.br). On this
393	// PHP serve path the web server never sees the .br, so without
394	// this a br-capable client got the plain .html — precompression
395	// did nothing here. Falls through to plain readfile otherwise.
396	$br = self::maybe_serve_brotli( $file );
397	if ( null !== $br ) {
398	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_readfile -- streaming a static cache file directly; WP_Filesystem would buffer through PHP memory and is not appropriate for response streaming.
399	readfile( $br );
400	exit;
401	}
402	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_readfile -- readfile is optimal for streaming a static cache file directly to the visitor; WP_Filesystem would buffer through PHP memory and is not appropriate for response streaming.
403	readfile( $file );
404	exit;
405	}
406
407	// Cache miss → render fresh + write cache. On LiteSpeed we send an
408	// explicit "stand down" header so the server's LSCache module does
409	// NOT cache + shadow our response — xSpeed's own .htaccess static
410	// rewrite owns hit serving (and hit accounting) here, exactly as on
411	// Apache. See maybe_emit_lscache_headers() for the full rationale.
412	self::maybe_emit_lscache_headers();
413
414	// We're about to render fresh + cache → miss for this request.
415	// …UNLESS this request is a 404 or a known bot/scanner. Those reach the
416	// render path too, but counting them as cache misses makes the ratio
417	// meaningless — a wave of `/wp-x7.php` scanner 404s reads as a collapsing
418	// cache when nothing is wrong. Runs at template_redirect (priority 0), so
419	// is_404() is already resolved. Excluded requests are tallied separately
420	// for the "you absorbed N scanner hits" line, not dropped. (#118)
421	if ( self::miss_is_excluded() ) {
422	Hit_Counter::record_excluded();
423	} else {
424	Hit_Counter::record_miss();
425	}
426
427	// Stamp it, so "eligible but not cached yet" is visibly different
428	// from "deliberately bypassed" (issue #10). Headers can't be sent
429	// after the body starts, so this has to happen here, not in
430	// finalize_buffer() — nothing has been output at template_redirect.
431	self::mark( 'MISS' );
432
433
434	// WP < 6.9 fallback: ob_start() with a callback, paired with an
435	// explicit shutdown close so the buffer lifecycle is visible to
436	// reviewers and Plugin Check, instead of relying on PHP's implicit
437	// request-end flush. We record our nesting level so close_buffer()
438	// flushes ONLY the buffer we opened.
439	ob_start( array( __CLASS__, 'finalize_buffer' ) );
440	self::$buffer_level = ob_get_level();
441
442	add_action( 'shutdown', array( __CLASS__, 'close_buffer' ), 0 );
443	}
444
445	/**
446	* Close the cache buffer opened by maybe_start_cache().
447	*
448	* Guarded by the recorded buffer level so we never flush a buffer that
449	* another plugin pushed on top of (or under) ours. If something else is
450	* currently on top, we leave the stack alone — PHP's shutdown sequence
451	* will unwind buffers in order and our finalize_buffer() callback will
452	* still run when our level becomes the topmost one.
453	*/
454	public static function close_buffer() {
455	if ( null === self::$buffer_level ) {
456	return;
457	}
458	if ( ob_get_level() === self::$buffer_level ) {
459	ob_end_flush();
460	}
461	self::$buffer_level = null;
462	}
463
464	/**
465	* Are we buffering this request?
466	*
467	* Asked by Css_Combine_Buffer, which needs the finished HTML but must not
468	* open a second buffer when this one is already going to hand it the page
469	* through `xspeed_cache_final_html`. False here means the request is not
470	* cacheable — cache off, excluded URL, logged in — and the combiner has to
471	* provide its own buffer or it silently stops working. (#195)
472	*/
473	public static function is_buffering(): bool {
474	return null !== self::$buffer_level;
475	}
476
477	/**
478	* Is a render-time translation plugin going to wrap our output buffer?
479	*
480	* TranslatePress opens its translation buffer on `init` priority 0. We
481	* open ours on `template_redirect`, which runs much later, so ours nests
482	* INSIDE theirs. PHP unwinds output buffers LIFO — innermost callback
483	* first — so `finalize_buffer()` saw the raw, pre-translation HTML and
484	* cached that, while the live visitor still got the translated bytes from
485	* TRP's outer buffer.
486	*
487	* Result: the first (MISS) visitor to /fr/some-page/ got correct French;
488	* every visitor after got English body text under a `lang="fr-FR"`
489	* document, plus TRP's internal `#TRPLINKPROCESSED` link markers, which
490	* TRP strips at the very end of its own buffer and which therefore leak
491	* into anything captured from inside it.
492	*
493	* Note the ordering cannot be fixed from TRP's side: its
494	* `trp_start_output_buffer_priority` filter only moves the PRIORITY on
495	* `init`, and `init` always fires before `template_redirect` whatever the
496	* priority. The buffer that has to move is ours.
497	*
498	* Detected by main class rather than plugin path, so a renamed directory
499	* or a bundled copy still matches.
500	*/
501	public static function translation_plugin_active(): bool {
502	$active = class_exists( 'TRP_Translate_Press' );
503
504	/**
505	* Whether to treat this request as wrapped by a translation buffer.
506	*
507	* Lets a site add another render-time translation plugin (or opt out)
508	* without patching the engine.
509	*
510	* @param bool $active
511	*/
512	return (bool) apply_filters( 'xspeed_translation_plugin_active', $active );
513	}
514
515	/**
516	* Write the cache file for a request whose output was wrapped by a
517	* render-time translation plugin.
518	*
519	* Registered as a PHP shutdown function (not a WP `shutdown` action) so
520	* it runs after PHP has unwound the output-buffer stack — by which point
521	* the translation plugin's callback has transformed the bytes and its
522	* internal markers are gone.
523	*
524	* finalize_buffer() has already applied the status gate, the
525	* xspeed_cache_final_html filter and HTML minification to the
526	* untranslated copy and then declined to write it. Here we re-run only
527	* what's needed on the translated bytes: minify, write, and fire the
528	* same downstream hooks so Brotli / static-tree listeners behave
529	* identically to the ordinary path.
530	*/
531	public static function write_deferred_translated_cache(): void {
532	$key = self::$deferred_key;
533	self::$deferred_key = null;
534
535	// Release the collected bytes BEFORE the early return, so the static
536	// is cleared on every path rather than only when a key survived.
537	$full = self::$translated_output;
538	self::$translated_output = '';
539
540	$completed = self::$render_completed;
541	self::$render_completed = false;
542
543	if ( null === $key ) {
544	return;
545	}
546
547	// Did the render actually finish?
548	//
549	// This runs as a PHP shutdown function, which fires after a wp_die()
550	// or a bare exit() just as readily as after a clean render — but in
551	// those cases finalize_buffer() never returned, so the bytes we hold
552	// are a page that was cut off partway through. The length and
553	// TRPLINKPROCESSED checks below don't catch that: a fatal after the
554	// footer's translated markup is both over 255 bytes and free of TRP
555	// markers, i.e. truncated but entirely plausible. Caching it would
556	// freeze a half-rendered page under the real key for the full TTL.
557	//
558	// Serving this one URL uncached is the cheap failure; the corrupt
559	// cache entry is the expensive one.
560	if ( ! $completed ) {
561	return;
562	}
563
564	if ( strlen( $full ) < 255 ) {
565	return;
566	}
567
568	// Refuse to cache a copy still carrying the translation plugin's
569	// internal link markers. TRP strips these at the very end of its own
570	// buffer, so their presence means we captured too early — and a
571	// cached page containing them is SEO-visible damage. Better to serve
572	// this URL uncached than to freeze broken markup for the full TTL.
573	if ( false !== strpos( $full, 'TRPLINKPROCESSED' ) ) {
574	return;
575	}
576
577	$minify_opts = Settings_Manager::get( 'minify' );
578	if ( ! empty( $minify_opts['minify_html'] ) ) {
579	$full = Minifier::minify_html( $full );
580	}
581
582	// Per-site directory: on multisite every blog shares this tree, so
583	// entries are bucketed by host to keep one site's purge from
584	// sweeping the whole network. (#6)
585	self::ensure_host_dir();
586
587	$file = self::cache_file_for( $key );
588	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents -- WP_Filesystem requires admin context for credentials; this runs on a frontend shutdown where it's unavailable.
589	file_put_contents( $file, $full, LOCK_EX );
590
591	/** This action is documented in includes/class-cache.php */
592	do_action( 'xspeed_flat_file_written', $file, $full );
593
594	self::write_meta( $key );
595
596	// Static tree too, under the same gates finalize_buffer() applies —
597	// otherwise deferring the write would silently cost translated pages
598	// the web-server fast path and leave them on the slower drop-in.
599	if ( self::static_rewrite_allowed() && self::response_is_plain_html() ) {
600	self::store_static( $full );
601	}
602	}
603
604	public static function should_cache() {
605	// Reset first: a single request only reaches this once (the sole
606	// caller is maybe_start_cache()), but tests and any future caller
607	// must never inherit the previous request's verdict.
608	self::$status_header = '';
609	self::$bypass_reason = '';
610
611	$opts = Settings::get();
612	if ( empty( $opts['cache_enabled'] ) ) {
613	return self::bypass( 'cache-disabled' );
614	}
615
616	if ( is_user_logged_in() ) {
617	return self::bypass( 'logged-in' );
618	}
619
620	if ( is_admin() \|\| ( defined( 'DOING_AJAX' ) && DOING_AJAX ) \|\| ( defined( 'DOING_CRON' ) && DOING_CRON ) \|\| ( defined( 'REST_REQUEST' ) && REST_REQUEST ) ) {
621	return self::bypass( 'non-frontend' );
622	}
623
624	if ( defined( 'DONOTCACHEPAGE' ) && DONOTCACHEPAGE ) {
625	return self::bypass( 'donotcachepage' );
626	}
627
628	// All exclusion knobs now owned by CacheModule.
629	$cache_opts = Settings_Manager::get( 'cache' );
630
631	$method = isset( $_SERVER['REQUEST_METHOD'] ) ? strtoupper( sanitize_text_field( wp_unslash( $_SERVER['REQUEST_METHOD'] ) ) ) : '';
632	if ( 'GET' !== $method ) {
633	return self::bypass( 'non-get' );
634	}
635
636	// Search-results requests carry a `s` query param, which the
637	// query-string gate below would normally reject as "dynamic". An
638	// add-on (xspeed-pro search cache) can opt them in: when this is a
639	// genuine is_search() and the filter returns true, the `s` param is
640	// treated as cacheable (the search term goes into the cache key so
641	// different searches stay distinct — see cache_key()).
642	$cache_search = self::should_cache_search();
643
644	// Feed opt-in is resolved BEFORE the query-string gate so query-form
645	// feeds (/?feed=rss2, used on plain-permalink sites) aren't rejected
646	// as "dynamic" by that gate — the `feed` param is then allowed through
647	// just like the search `s` param. Feeds are excluded by default (the
648	// `/feed/` pattern in excluded_urls); an add-on (xspeed-pro feed cache)
649	// opts them back in via the filter. (FBS-82407 #4)
650	$is_feed_request = function_exists( 'is_feed' ) && is_feed();
651	/**
652	* Whether to cache the current feed request.
653	*
654	* Default false → feeds fall through to the normal URL-exclusion
655	* rules (so `/feed/` keeps them out). A listener returning true
656	* opts this feed request into caching.
657	*
658	* @param bool $cache_feed Whether to cache this feed request.
659	*/
660	$cache_feed = $is_feed_request && (bool) apply_filters( 'xspeed_should_cache_feed', false );
661
662	// Query string handling: anything OUTSIDE the ignored-params
663	// allow-list (utm_*, fbclid, gclid by default) means a unique
664	// request that we don't want to share with the canonical cache
665	// entry. Skip cache rather than poison the key.
666	//
667	// Parse the RAW query string, NOT a sanitize_text_field() copy:
668	// that filter strips percent-encoded octets (%XX), so `?%73=…`
669	// would lose its `s` key here while WordPress still decodes it to
670	// a search request — the gate would wave the request through and
671	// cache_key() would file the search page under the bare URL,
672	// letting an attacker poison the homepage cache with `/?%73=<spam>`.
673	// parse_str() does its own urldecoding, matching WP's own parse, and
674	// only the KEYS are used below (fed to Glob_Matcher → preg_match,
675	// never echoed or executed), so no sanitization is needed here.
676	$query_raw = isset( $_SERVER['QUERY_STRING'] ) ? wp_unslash( $_SERVER['QUERY_STRING'] ) : ''; // phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotSanitized -- see note above: parse_str() urldecodes to match WP; only keys are consumed, via preg_match, never output.
677	if ( '' !== $query_raw ) {
678	$ignored = is_array( $cache_opts['ignored_query_params'] ?? null ) ? $cache_opts['ignored_query_params'] : array();
679	parse_str( $query_raw, $params );
680	foreach ( $params as $key => $_ ) {
681	// Allow the search param through when search caching is on.
682	if ( $cache_search && 's' === $key ) {
683	continue;
684	}
685	// Allow query-form feed params through when feed caching opted
686	// this request in (?feed=rss2 / &withcomments=1 on feeds).
687	if ( $cache_feed && in_array( $key, array( 'feed', 'withcomments', 'withoutcomments' ), true ) ) {
688	continue;
689	}
690	if ( ! self::query_key_is_ignored( (string) $key, $ignored ) ) {
691	// Slug only — never the param name, which is attacker-
692	// controlled and would be reflected into a header.
693	return self::bypass( 'query-param' );
694	}
695	}
696	}
697
698	$request_uri = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '';
699	$path = (string) strtok( $request_uri, '?' );
700
701	$excluded_urls = is_array( $cache_opts['excluded_urls'] ?? null ) ? $cache_opts['excluded_urls'] : array();
702	if ( ! $cache_feed && Glob_Matcher::any_match( $excluded_urls, $path ) ) {
703	return self::bypass( 'excluded-url' );
704	}
705
706	// Cookie-based exclusion. We only check cookie NAMES (matching
707	// values would leak content-sensitive logic into the cache key
708	// rules); presence of any matching cookie name skips cache.
709	$excluded_cookies = is_array( $cache_opts['excluded_cookies'] ?? null ) ? $cache_opts['excluded_cookies'] : array();
710	if ( ! empty( $excluded_cookies ) && ! empty( $_COOKIE ) ) {
711	foreach ( array_keys( $_COOKIE ) as $cookie_name ) {
712	// Our own bypass cookie is a RECORD of a previous verdict, not
713	// evidence about this visitor, so it never gets a vote here.
714	// Letting it match made the verdict self-confirming: once set,
715	// it produced `excluded-cookie` forever, which re-set it, and
716	// no later request could ever re-evaluate the visitor on the
717	// rules that actually describe them. The web server still acts
718	// on the cookie without booting PHP; when PHP does boot it is
719	// authoritative and re-decides from scratch. (#218)
720	if ( Server_Rules::BYPASS_COOKIE === $cookie_name ) {
721	continue;
722	}
723	if ( Glob_Matcher::any_match( $excluded_cookies, (string) $cookie_name ) ) {
724	return self::bypass( 'excluded-cookie' );
725	}
726	}
727	}
728
729	// User-agent bypass list. Substring match (not glob) since UA
730	// strings have so much variation that glob anchoring rarely
731	// helps and confuses users.
732	$bypass_uas = is_array( $cache_opts['bypass_user_agents'] ?? null ) ? $cache_opts['bypass_user_agents'] : array();
733	if ( ! empty( $bypass_uas ) ) {
734	$ua = isset( $_SERVER['HTTP_USER_AGENT'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_USER_AGENT'] ) ) : '';
735	foreach ( $bypass_uas as $needle ) {
736	if ( '' !== $needle && false !== stripos( $ua, (string) $needle ) ) {
737	return self::bypass( 'user-agent' );
738	}
739	}
740	}
741
742	// Per-post override (Phase 3.4). Honored only on singular
743	// post-context requests — archives / 404s / taxonomies use the
744	// global policy above.
745	if ( Cache_Rules::should_skip_for_post( Cache_Rules::current_post_id() ) ) {
746	return self::bypass( 'post-excluded' );
747	}
748
749	/**
750	* Final say on whether the current request is cacheable.
751	*
752	* Runs at template_redirect (full WP context), so listeners may use
753	* conditional tags (is_search(), is_feed(), is_404(),
754	* wp_is_maintenance_mode(), …). The core engine has already applied
755	* its own exclusion rules and reached `true`; a listener returning
756	* false vetoes caching for this request. This is the documented
757	* extension point add-ons (xspeed-pro) hook to add their own
758	* request-level cache policy without forking the engine.
759	*
760	* Note: this gates the WRITE side. The pre-WP drop-in
761	* (advanced-cache.php) cannot run PHP filters, so request types that
762	* must never be served from a stale file are handled by not
763	* writing them here and/or by purging — see the conflict notes in
764	* advanced-cache.php.
765	*
766	* @param bool $should_cache Whether to cache the current request.
767	*/
768	if ( ! apply_filters( 'xspeed_should_cache', true ) ) {
769	// One slug for every listener — a third-party callback name is
770	// not ours to put in a response header. Which listener vetoed is
771	// a WP_DEBUG-level question the filter itself can answer.
772	return self::bypass( 'filtered' );
773	}
774
775	return true;
776	}
777
778	/**
779	* Whether the current request is a 404 we may cache.
780	*
781	* True only when: it's a genuine main-query is_404(), an add-on opted
782	* in via `xspeed_should_cache_404` (default false), and the request
783	* isn't a transient 404 we must never freeze — maintenance mode or a
784	* 404 emitted while the DB/site is in an error state. The xspeed-pro
785	* 404 cache flips the filter; Free never caches 404s on its own.
786	*/
787	public static function should_cache_404(): bool {
788	if ( ! function_exists( 'is_404' ) \|\| ! is_404() ) {
789	return false;
790	}
791	// Never cache a 404 served because the site is down for
792	// maintenance — that screen disappears the moment maintenance
793	// ends, and a cached copy would outlive it.
794	if ( function_exists( 'wp_is_maintenance_mode' ) && wp_is_maintenance_mode() ) {
795	return false;
796	}
797
798	/**
799	* Whether to cache the current 404 response.
800	*
801	* Default false. A listener returning true opts the (genuine)
802	* 404 into the page cache, served back for any unknown URL under
803	* one generic key. The 404 status is preserved on the HIT.
804	*
805	* @param bool $cache_404 Whether to cache this 404.
806	*/
807	return (bool) apply_filters( 'xspeed_should_cache_404', false );
808	}
809
810	/**
811	* Whether the current request is an internal search-results page we
812	* may cache.
813	*
814	* True only when: it's a genuine main-query is_search() with a
815	* non-empty term, and an add-on opted in via `xspeed_should_cache_search`
816	* (default false). The search term is folded into the cache key (see
817	* search_term() / cache_key()) so different searches stay distinct.
818	* The xspeed-pro search cache flips the filter; Free never caches
819	* search results on its own.
820	*/
821	public static function should_cache_search(): bool {
822	if ( ! function_exists( 'is_search' ) \|\| ! is_search() ) {
823	return false;
824	}
825	// Empty search (`?s=`) renders the same as a normal archive and
826	// carries no term to key on — let it fall through to the usual
827	// rules rather than caching an ambiguous entry.
828	if ( '' === self::search_term() ) {
829	return false;
830	}
831
832	/**
833	* Whether to cache the current search-results request.
834	*
835	* Default false. A listener returning true opts the search page
836	* into the cache, keyed by the normalized search term.
837	*
838	* @param bool $cache_search Whether to cache this search request.
839	*/
840	return (bool) apply_filters( 'xspeed_should_cache_search', false );
841	}
842
843	/**
844	* The current request's normalized search term, or '' if none. Reads
845	* the raw `s` query param (works on the pre-WP drop-in path too, where
846	* get_search_query() isn't available), trims + lowercases so
847	* "WordPress" and "wordpress" share one entry, and collapses internal
848	* whitespace.
849	*/
850	public static function search_term(): string {
851	$raw = isset( $_GET['s'] ) ? sanitize_text_field( wp_unslash( $_GET['s'] ) ) : ''; // phpcs:ignore WordPress.Security.NonceVerification.Recommended -- read-only cache-key derivation from a public search param; no state change.
852	$raw = trim( $raw );
853	if ( '' === $raw ) {
854	return '';
855	}
856	$raw = preg_replace( '/\s+/', ' ', $raw );
857	return function_exists( 'mb_strtolower' ) ? mb_strtolower( $raw ) : strtolower( $raw );
858	}
859
860	/**
861	* Is this query-string key on the ignored-params allow-list? Supports
862	* trailing-star globs (`utm_*` matches `utm_source`, `utm_medium`,
863	* etc.) so users don't have to enumerate every UTM variant.
864	*/
865	private static function query_key_is_ignored( string $key, array $ignored ): bool {
866	return Glob_Matcher::any_match( $ignored, $key );
867	}
868
869	public static function cache_key() {
870	$host = isset( $_SERVER['HTTP_HOST'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_HOST'] ) ) : 'default';
871
872	// Cacheable 404s share ONE generic per-host entry — keying them by
873	// URL would let a scanner flood (millions of random paths) bloat
874	// the cache with identical 404 bodies. Both the write and the HIT
875	// lookup run through here, so they agree on the key automatically.
876	if ( self::should_cache_404() ) {
877	return md5( $host . '\|404' );
878	}
879
880	$uri = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '/';
881	// Strip the query string from the key so /post and /post?utm_*=…
882	// share the same cache entry. should_cache() above already
883	// rejected requests with non-ignored params, so by the time we
884	// build the key the only params left are safe to drop.
885	$uri = (string) strtok( $uri, '?' );
886
887	// Optional device bucket: when mobile_separate is on, mobile and
888	// desktop responses live in different cache files so themes that
889	// serve different HTML by device (AMP, WPtouch, Jetpack mobile)
890	// can't poison each other.
891	$device = '';
892	$opts = Settings_Manager::get( 'cache' );
893	if ( ! empty( $opts['mobile_separate'] ) ) {
894	$device = self::is_mobile_request() ? '\|m' : '\|d';
895	}
896
897	// Search-results requests fold the normalized term into the key so
898	// /?s=foo and /?s=bar get distinct entries (the query string is
899	// otherwise stripped above). Only added when search caching opted
900	// in, so non-search URLs are unaffected.
901	$search = self::should_cache_search() ? '\|s=' . self::search_term() : '';
902
903	// Query-form feeds (/?feed=rss2 vs /?feed=atom) share the same path
904	// once the query is stripped, so fold the feed type into the key to
905	// keep the flavors distinct. Pretty-permalink feeds (/feed/rss/) carry
906	// the type in $uri already and are unaffected. (FBS-82407 #4)
907	$feed = '';
908	if ( function_exists( 'is_feed' ) && is_feed() && function_exists( 'get_query_var' ) ) {
909	$feed_type = (string) get_query_var( 'feed' );
910	if ( '' !== $feed_type ) {
911	$feed = '\|feed=' . preg_replace( '/[^a-z0-9]/i', '', $feed_type );
912	}
913	}
914
915	return md5( $host . $uri . $device . $search . $feed );
916	}
917
918	/**
919	* Server-side mobile detection. Prefers WordPress's `wp_is_mobile()`
920	* which uses the same UA tokens as core (so our bucket aligns with
921	* whatever theme-side branching uses). Falls back to a tiny inline
922	* detector if wp_is_mobile() isn't loaded (e.g. the drop-in path).
923	*/
924	private static function is_mobile_request(): bool {
925	if ( function_exists( 'wp_is_mobile' ) ) {
926	return (bool) wp_is_mobile();
927	}
928	// Fallback for the rare context where wp_is_mobile() isn't loaded.
929	// Mirrors core's wp_is_mobile() EXACTLY — including the
930	// Sec-CH-UA-Mobile client hint it checks before UA tokens — so the
931	// bucket this picks matches whatever the engine's primary path (and
932	// the drop-in's own copy of this logic) would pick for the same
933	// request. Drift here re-introduces the cross-path key mismatch.
934	if ( isset( $_SERVER['HTTP_SEC_CH_UA_MOBILE'] ) ) {
935	return '?1' === $_SERVER['HTTP_SEC_CH_UA_MOBILE'];
936	}
937	$ua = isset( $_SERVER['HTTP_USER_AGENT'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_USER_AGENT'] ) ) : '';
938	if ( '' === $ua ) {
939	return false;
940	}
941	return (bool) preg_match( '/(Mobile\|Android\|Silk\/\|Kindle\|BlackBerry\|Opera Mini\|Opera Mobi)/i', $ua );
942	}
943
944	/**
945	* Filesystem-safe directory name for a host, or '' when unusable.
946	*
947	* The charset MUST match the static tree (store_static()) and the
948	* drop-in's own copy, or the paths disagree about where an entry lives.
949	* The colon of `host:port` is stripped: it is legal in a Host header but
950	* not portable in a path.
951	*
952	* @param string $host Raw host, e.g. from HTTP_HOST.
953	* @return string Safe directory segment, or '' if nothing usable remains.
954	*/
955	public static function host_dir( string $host ): string {
956	$host = str_replace( "\0", '', $host );
957	// Drop the port BEFORE filtering, or `example.com:8080` collapses to
958	// `example.com8080` — which both loses the boundary and could collide
959	// with a real host of that name.
960	$colon = strpos( $host, ':' );
961	if ( false !== $colon ) {
962	$host = substr( $host, 0, $colon );
963	}
964	$host = preg_replace( '/[^a-zA-Z0-9.\-]/', '', $host );
965	// Collapse any run of dots so no traversal sequence can survive the
966	// charset filter (`a/../b` would otherwise reduce to `a..b`).
967	$host = preg_replace( '/\.{2,}/', '.', (string) $host );
968	$host = trim( (string) $host, '.-' );
969	return '' === $host ? '' : $host;
970	}
971
972	/**
973	* The per-site bucket a cache entry belongs to: `<host>` on a single
974	* site, `<host>/<path-prefix>` for a subdirectory multisite blog.
975	*
976	* On multisite every blog shares one cache directory, and a flat md5
977	* filename carries no clue which site wrote it — so purging one subsite
978	* swept the whole network cold. (#6)
979	*
980	* Host alone is NOT enough: a subdirectory network (the common layout)
981	* puts every blog on the same host, so `example.com/` and
982	* `example.com/siteb/` would share a bucket and keep purging each other.
983	* The path prefix is what separates them, and it is derivable from the
984	* REQUEST_URI alone — which matters because the drop-in must compute
985	* this identical value before WordPress (and get_blog_details()) exist.
986	*
987	* Subdomain and domain-mapped networks differ by host already, so they
988	* get a bare host bucket and are unaffected.
989	*
990	* @param string $host Raw host.
991	* @param string $uri Raw REQUEST_URI (query string is ignored).
992	* @return string Bucket path, always non-empty.
993	*/
994	public static function site_bucket( string $host, string $uri ): string {
995	$dir = self::host_dir( $host );
996	if ( '' === $dir ) {
997	$dir = 'default';
998	}
999
1000	$prefix = self::site_path_prefix();
1001	return '' === $prefix ? $dir : $dir . '/' . $prefix;
1002	}
1003
1004	/**
1005	* The current blog's path prefix as a single safe segment ('' for the
1006	* root blog or a non-multisite install). `/siteb/` becomes `siteb`;
1007	* a nested `/a/b/` becomes `a-b` so the bucket stays one level deep.
1008	*
1009	* Written to a sidecar for the drop-in by sync_site_paths().
1010	*/
1011	public static function site_path_prefix(): string {
1012	if ( ! function_exists( 'is_multisite' ) \|\| ! is_multisite() ) {
1013	return '';
1014	}
1015	if ( function_exists( 'is_subdomain_install' ) && is_subdomain_install() ) {
1016	return ''; // Hosts already differ; no prefix needed.
1017	}
1018	$path = function_exists( 'get_blog_details' ) ? (string) get_blog_details()->path : '/';
1019	return self::path_prefix_segment( $path );
1020	}
1021
1022	/**
1023	* The bucket an arbitrary URL's cache entry lives in.
1024	*
1025	* `site_bucket()` answers for the CURRENT request; this answers for a URL
1026	* that may belong to another blog entirely — which is what a per-URL purge
1027	* is usually doing (WP-CLI, cron, the MCP tool, a network-admin action).
1028	*
1029	* The blog is resolved from the URL itself: on a subdirectory network
1030	* `get_blog_details()` is asked which blog owns `<host><path>`, and its
1031	* registered path becomes the prefix. Deriving the prefix from the URL's
1032	* first path segment directly would be wrong — `/shop/` on the main blog
1033	* is a page, not a subsite, and would send the purge into a bucket that
1034	* does not exist. (QA B2 on #166)
1035	*
1036	* @param string $host Host of the URL being purged.
1037	* @param string $path Path of the URL being purged.
1038	* @return string Bucket path, always non-empty.
1039	*/
1040	public static function bucket_for_url( string $host, string $path ): string {
1041	$dir = self::host_dir( $host );
1042	if ( '' === $dir ) {
1043	$dir = 'default';
1044	}
1045
1046	if ( ! function_exists( 'is_multisite' ) \|\| ! is_multisite() ) {
1047	return $dir;
1048	}
1049	if ( function_exists( 'is_subdomain_install' ) && is_subdomain_install() ) {
1050	return $dir; // Hosts already differ; no prefix.
1051	}
1052	if ( ! function_exists( 'get_blog_details' ) ) {
1053	return $dir;
1054	}
1055
1056	// Longest registered blog path that prefixes this URL wins, so
1057	// `/one/2026/post/` resolves to blog `/one/` and not to the root blog.
1058	$blog = self::blog_for_path( $host, $path );
1059	if ( null === $blog ) {
1060	return $dir;
1061	}
1062	$prefix = self::path_prefix_segment( (string) $blog );
1063	return '' === $prefix ? $dir : $dir . '/' . $prefix;
1064	}
1065
1066	/**
1067	* The registered path of the blog that owns `<host><path>`, or null.
1068	*
1069	* Uses get_blog_details() with a domain/path pair rather than scanning
1070	* every blog, so a large network costs one lookup per candidate segment
1071	* instead of a full table read.
1072	*/
1073	private static function blog_for_path( string $host, string $path ): ?string {
1074	$segments = array_values( array_filter( explode( '/', trim( $path, '/' ) ) ) );
1075
1076	// Try the longest candidate first: /a/b/ before /a/ before /.
1077	for ( $take = min( count( $segments ), 2 ); $take >= 1; $take-- ) {
1078	$candidate = '/' . implode( '/', array_slice( $segments, 0, $take ) ) . '/';
1079	$details = get_blog_details(
1080	array(
1081	'domain' => $host,
1082	'path' => $candidate,
1083	),
1084	false
1085	);
1086	if ( $details && ! empty( $details->path ) ) {
1087	return (string) $details->path;
1088	}
1089	}
1090	return null;
1091	}
1092
1093	/**
1094	* Normalise a blog path ('/', '/siteb/', '/a/b/') into a single
1095	* filesystem-safe segment. Shared with the drop-in's copy.
1096	*/
1097	public static function path_prefix_segment( string $path ): string {
1098	$path = trim( str_replace( "\0", '', $path ), '/' );
1099	if ( '' === $path ) {
1100	return '';
1101	}
1102	$path = preg_replace( '/[^a-zA-Z0-9._\-\/]/', '', $path );
1103	$path = str_replace( '/', '-', (string) $path );
1104	return trim( (string) $path, '.-' );
1105	}
1106
1107	/**
1108	* The current blog's path as the static tree stores it — real slashes
1109	* preserved, because that tree mirrors the URL
1110	* (`xspeed-static/{host}{request_uri}/index.html`) rather than using a
1111	* single flattened segment. '' for a root blog / single site.
1112	*/
1113	public static function site_path_raw(): string {
1114	if ( ! function_exists( 'is_multisite' ) \|\| ! is_multisite() ) {
1115	return '';
1116	}
1117	if ( function_exists( 'is_subdomain_install' ) && is_subdomain_install() ) {
1118	return '';
1119	}
1120	$path = function_exists( 'get_blog_details' ) ? (string) get_blog_details()->path : '/';
1121	$path = trim( str_replace( "\0", '', $path ), '/' );
1122	if ( '' === $path ) {
1123	return '';
1124	}
1125	$path = preg_replace( '#[^a-zA-Z0-9._\-/]#', '', $path );
1126	return trim( (string) $path, '/' );
1127	}
1128
1129	/**
1130	* Static-tree root for the current site: `<host>` plus the blog's real
1131	* path. Mirrors store_static()'s layout so a scoped purge deletes
1132	* exactly this blog's pages.
1133	*/
1134	public static function current_static_scope(): string {
1135	// Same switch_to_blog() caveat as current_host_dir() — see current_host().
1136	$dir = self::host_dir( self::current_host() );
1137	if ( '' === $dir ) {
1138	$dir = 'default';
1139	}
1140	$path = self::site_path_raw();
1141	return '' === $path ? $dir : $dir . '/' . $path;
1142	}
1143
1144	/**
1145	* The bucket for the CURRENT request. Never empty, so an entry is never
1146	* written to the tree root (which is what the unscoped sweeps used to
1147	* delete indiscriminately).
1148	*/
1149	public static function current_host_dir(): string {
1150	$host = self::current_host();
1151	$uri = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '/';
1152	return self::site_bucket( $host, $uri );
1153	}
1154
1155	/**
1156	* The host the CURRENT blog is served from.
1157	*
1158	* Deliberately NOT just $_SERVER['HTTP_HOST']: inside a
1159	* switch_to_blog() the request header still names whichever site is
1160	* serving the admin screen, while the cache entries we want belong to
1161	* the switched-to blog. On a subdomain network the host IS the bucket,
1162	* so reading the header there would make Pro's per-site "purge this
1163	* site" button clear the network admin's own cache instead — the very
1164	* bug this scoping exists to fix, surviving in one topology.
1165	*
1166	* get_blog_details() follows the switch, so prefer it whenever we are
1167	* on multisite, and fall back to the request header otherwise.
1168	*/
1169	public static function current_host(): string {
1170	if ( function_exists( 'is_multisite' ) && is_multisite() && function_exists( 'get_blog_details' ) ) {
1171	$details = get_blog_details();
1172	if ( $details && ! empty( $details->domain ) ) {
1173	return (string) $details->domain;
1174	}
1175	}
1176
1177	if ( isset( $_SERVER['HTTP_HOST'] ) ) {
1178	return sanitize_text_field( wp_unslash( $_SERVER['HTTP_HOST'] ) );
1179	}
1180
1181	/*
1182	* No request header — WP-CLI, or WP-Cron driven by system cron.
1183	*
1184	* Returning '' here made the bucket resolve to the literal `default`
1185	* while HTTP requests were writing to `<host>/`, so a scheduled purge
1186	* swept an empty directory and reported success, and get_stats()
1187	* reported 0 cached pages on a site with a full cache. That is the
1188	* normal setup on any host running DISABLE_WP_CRON, which is most of
1189	* them. Fall back to the site's own registered host. (QA D4 on #166)
1190	*/
1191	if ( function_exists( 'home_url' ) ) {
1192	$parts = function_exists( 'wp_parse_url' ) ? wp_parse_url( home_url( '/' ) ) : parse_url( home_url( '/' ) ); // phpcs:ignore WordPress.WP.AlternativeFunctions.parse_url_parse_url -- early-boot fallback only.
1193	if ( is_array( $parts ) && ! empty( $parts['host'] ) ) {
1194	return (string) $parts['host'];
1195	}
1196	}
1197
1198	return '';
1199	}
1200
1201	/**
1202	* Ensure the current site's cache directory exists, with the silence
1203	* index in both it and the shared root. Returns the directory.
1204	*/
1205	public static function ensure_host_dir(): string {
1206	$dir = XSPEED_CACHE_DIR . '/' . self::current_host_dir();
1207	if ( ! file_exists( XSPEED_CACHE_DIR ) ) {
1208	wp_mkdir_p( XSPEED_CACHE_DIR );
1209	self::write_silence( XSPEED_CACHE_DIR );
1210	}
1211	if ( ! file_exists( $dir ) ) {
1212	wp_mkdir_p( $dir );
1213	self::write_silence( $dir );
1214	}
1215	return $dir;
1216	}
1217
1218	public static function cache_file_for( $key ) {
1219	return XSPEED_CACHE_DIR . '/' . self::current_host_dir() . '/' . $key . '.html';
1220	}
1221
1222	/**
1223	* If a precompressed Brotli sibling (`<file>.br`) exists and the client
1224	* advertises `Accept-Encoding: br`, emit the Brotli response headers and
1225	* return the `.br` path to stream. Returns null to fall through to the
1226	* plain file. Keeps the PHP serve path in parity with the web server's
1227	* static .br serving (mod_brotli / ngx_brotli rewrite).
1228	*
1229	* Free has no Brotli logic of its own — this only fires when an add-on
1230	* (the Pro Brotli module) actually wrote the .br, so it's a safe no-op
1231	* on Free-only installs.
1232	*
1233	* @param string $file Absolute path to the cached .html file.
1234	* @return string\|null The .br path to stream, or null to serve $file.
1235	*/
1236	public static function maybe_serve_brotli( string $file ): ?string {
1237	if ( headers_sent() ) {
1238	return null;
1239	}
1240	$accept = isset( $_SERVER['HTTP_ACCEPT_ENCODING'] )
1241	? strtolower( sanitize_text_field( wp_unslash( $_SERVER['HTTP_ACCEPT_ENCODING'] ) ) )
1242	: '';
1243	// Match `br` as a token (comma/space delimited), not a substring, so
1244	// a hypothetical "xbr" encoding can't false-positive.
1245	if ( ! preg_match( '/(^\|[\s,])br([\s,;]\|$)/', $accept ) ) {
1246	return null;
1247	}
1248	$br = $file . '.br';
1249	if ( ! is_string( $br ) \|\| ! file_exists( $br ) \|\| ! is_readable( $br ) ) {
1250	return null;
1251	}
1252	header( 'Content-Encoding: br' );
1253	header( 'Vary: Accept-Encoding', false );
1254	// The byte length changes for the compressed body — drop any
1255	// Content-Length the caller may have set so the stream isn't
1256	// truncated/padded. readfile() lets the SAPI set the right length.
1257	header_remove( 'Content-Length' );
1258	return $br;
1259	}
1260
1261	/**
1262	* Sidecar metadata file for a cache entry. Holds response bits the HIT
1263	* path must replay — Content-Type (cached feeds → application/rss+xml,
1264	* sitemaps → text/xml) and status (a cached 404 must serve 404, not
1265	* 200). JSON, one tiny file per entry, written only when there's
1266	* something non-default to replay.
1267	*/
1268	public static function cache_meta_for( $key ) {
1269	return XSPEED_CACHE_DIR . '/' . self::current_host_dir() . '/' . $key . '.meta';
1270	}
1271
1272	/**
1273	* Read the .meta sidecar for a cache entry as an array, or [] if none.
1274	* Keys: 'content_type' (string), 'status' (int), 'ttl' (int seconds).
1275	* Used on the HIT path to replay content-type/status before streaming
1276	* the file, and by Cache_GC to age an entry by its own TTL rather than
1277	* the global one — hence public.
1278	*/
1279	public static function read_meta( $key ): array {
1280	$meta_file = self::cache_meta_for( $key );
1281	if ( ! file_exists( $meta_file ) ) {
1282	return array();
1283	}
1284	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_get_contents_file_get_contents -- our own cache dir; WP_Filesystem needs admin creds unavailable on a frontend HIT.
1285	$raw = file_get_contents( $meta_file );
1286	$data = json_decode( (string) $raw, true );
1287	return is_array( $data ) ? $data : array();
1288	}
1289
1290	/**
1291	* Conditional-GET support for a cache HIT. Emits Last-Modified + ETag
1292	* derived from the cache file's mtime, and — when the request's
1293	* If-Modified-Since / If-None-Match still match — sends 304 Not Modified
1294	* and returns true (caller should exit without a body). Returns false to
1295	* proceed with a normal 200 body. Lets aggregators/browsers skip
1296	* re-downloading an unchanged cached response. (FBS-82407 #5)
1297	*
1298	* @param string $file Absolute path to the cache .html file.
1299	* @return bool True when a 304 was sent.
1300	*/
1301	public static function serve_not_modified( string $file ): bool {
1302	$mtime = (int) filemtime( $file );
1303	if ( $mtime <= 0 ) {
1304	return false;
1305	}
1306	$last_modified = gmdate( 'D, d M Y H:i:s', $mtime ) . ' GMT';
1307	$etag = '"' . md5( $file . '\|' . $mtime ) . '"';
1308	header( 'Last-Modified: ' . $last_modified );
1309	header( 'ETag: ' . $etag );
1310
1311	$ims = isset( $_SERVER['HTTP_IF_MODIFIED_SINCE'] ) ? trim( sanitize_text_field( wp_unslash( $_SERVER['HTTP_IF_MODIFIED_SINCE'] ) ) ) : '';
1312	$inm = isset( $_SERVER['HTTP_IF_NONE_MATCH'] ) ? trim( sanitize_text_field( wp_unslash( $_SERVER['HTTP_IF_NONE_MATCH'] ) ) ) : '';
1313
1314	$etag_match = '' !== $inm && false !== strpos( $inm, $etag );
1315	$time_match = '' !== $ims && ( strtotime( $ims ) >= $mtime );
1316
1317	if ( $etag_match \|\| $time_match ) {
1318	if ( function_exists( 'http_response_code' ) ) {
1319	http_response_code( 304 );
1320	}
1321	return true;
1322	}
1323	return false;
1324	}
1325
1326	public static function is_expired( $file ) {
1327	// cache_expiry now owned by CacheModule; per-post override
1328	// (Phase 3.4) shrinks the TTL further when the editor set one.
1329	$opts = Settings_Manager::get( 'cache' );
1330	$max_age = (int) $opts['cache_expiry'] * HOUR_IN_SECONDS;
1331	$post_override = Cache_Rules::expiry_override_seconds_for_post( Cache_Rules::current_post_id() );
1332	if ( null !== $post_override ) {
1333	$max_age = $post_override;
1334	}
1335
1336	/**
1337	* Filter the max-age (seconds) for the current cache entry.
1338	*
1339	* Lets an add-on apply a request-type-specific TTL — e.g. the
1340	* xspeed-pro feed cache gives feeds a longer expiry than pages,
1341	* since aggregators tolerate more staleness. Return seconds.
1342	*
1343	* @param int $max_age Computed max-age in seconds.
1344	*/
1345	$max_age = (int) apply_filters( 'xspeed_cache_max_age', $max_age );
1346
1347	// A missing file is "expired" — the caller should re-render. Guard
1348	// filemtime() rather than letting it warn: callers legitimately ask
1349	// about a file that isn't there (Pro's predictive warmer probes for
1350	// freshness, and Cache_GC can collect an entry between the check and
1351	// the read), and on a site with WP_DEBUG the warning is noise.
1352	$mtime = file_exists( $file ) ? filemtime( $file ) : false;
1353	if ( false === $mtime ) {
1354	return true;
1355	}
1356
1357	return ( time() - (int) $mtime ) > $max_age;
1358	}
1359
1360	/**
1361	* Accumulator for the full response body across all output-handler phases.
1362	*
1363	* PHP invokes an ob_start() callback once per flush, and each invocation
1364	* only receives the chunk produced since the previous flush. If anything
1365	* during the render calls `ob_flush()` or `flush()` (some themes, lazy-
1366	* load plugins, AMP, etc. do), the final-phase call would otherwise only
1367	* see the tail of the page — and we'd cache a truncated response that
1368	* gets served repeatedly until purge. We accumulate every chunk here so
1369	* the cache file always reflects the complete page.
1370	*
1371	* @var string
1372	*/
1373	private static $accumulated = '';
1374
1375	public static function finalize_buffer( $buffer, $phase = PHP_OUTPUT_HANDLER_FINAL ) {
1376	self::$accumulated .= $buffer;
1377
1378	// On non-final phases (mid-request flushes), pass the current chunk
1379	// through to the client unmodified and keep collecting. The WP 6.9
1380	// filter path always passes the full body in one shot with the
1381	// default $phase, so it falls straight through to the final block.
1382	$is_final = ( $phase & ( PHP_OUTPUT_HANDLER_FINAL \| PHP_OUTPUT_HANDLER_END ) ) !== 0;
1383	if ( ! $is_final ) {
1384	return $buffer;
1385	}
1386
1387	$full = self::$accumulated;
1388	self::$accumulated = '';
1389
1390	if ( strlen( $full ) < 255 ) {
1391	return $buffer;
1392	}
1393
1394	// Status gate. We cache 200 by default. A 404 may be cached too,
1395	// but only when an add-on (xspeed-pro 404 cache) opts in for a
1396	// genuine is_404() — never a transient 404 (maintenance screen,
1397	// DB error, or a 404 emitted outside the main query), which would
1398	// otherwise be frozen until purge. Any other status is skipped.
1399	$status = function_exists( 'http_response_code' ) ? (int) http_response_code() : 200;
1400	if ( 200 !== $status ) {
1401	if ( 404 !== $status \|\| ! self::should_cache_404() ) {
1402	return $buffer;
1403	}
1404	}
1405
1406	// If no mid-request flush happened, $buffer === $full and we can
1407	// safely minify the on-wire bytes too. Otherwise earlier chunks have
1408	// already been sent unminified, so we minify only what goes to disk —
1409	// the first visitor sees unminified HTML, every cache hit after that
1410	// is minified.
1411	$single_chunk = ( $buffer === $full );
1412
1413	/**
1414	* Filter: xspeed_cache_final_html
1415	*
1416	* Last chance to transform the fully-rendered page HTML before it is
1417	* minified and written to the cache file. Runs on cache MISS only, so
1418	* whatever a listener injects here is baked into the cached HTML and
1419	* replayed on every subsequent HIT (the drop-in short-circuits before
1420	* PHP on a HIT — a wp_head hook would never fire there).
1421	*
1422	* The Preload module uses this to inject the LCP-image <link rel=preload>
1423	* + preconnect hints and add fetchpriority="high" to the hero <img>.
1424	* Keep listeners fast and idempotent; this is the on-wire body.
1425	*
1426	* @param string $full Complete page HTML.
1427	*/
1428	$full = (string) apply_filters( 'xspeed_cache_final_html', $full );
1429	if ( $single_chunk ) {
1430	$buffer = $full;
1431	}
1432
1433	// minify_html now owned by the Minify module; read through the
1434	// module's storage so this stays consistent with the engine that
1435	// applies CSS/JS minification.
1436	$minify_opts = Settings_Manager::get( 'minify' );
1437	if ( ! empty( $minify_opts['minify_html'] ) ) {
1438	$full = Minifier::minify_html( $full );
1439	if ( $single_chunk ) {
1440	$buffer = $full;
1441	}
1442	}
1443
1444	// Per-site directory — see ensure_host_dir(). (#6)
1445	self::ensure_host_dir();
1446
1447	// Path safety: cache_file_for() builds
1448	// `XSPEED_CACHE_DIR . '/' . <host> . '/' . $key . '.html'` where $key
1449	// comes from md5() — guaranteed to be exactly 32 lowercase hex chars —
1450	// and <host> is filtered by host_dir() to [A-Za-z0-9.-] with leading
1451	// dots trimmed, so no traversal sequence ('..', '/', null byte, etc.)
1452	// can appear in either segment. The write is therefore always inside
1453	// XSPEED_CACHE_DIR.
1454	$key = self::cache_key();
1455	$file = self::cache_file_for( $key );
1456
1457	// A render-time translation plugin (TranslatePress) wraps our buffer,
1458	// so the bytes we hold here are still UNTRANSLATED — its callback has
1459	// not run yet, and writing now would cache English under a French URL
1460	// and bake in its internal #TRPLINKPROCESSED markers. Hand off to
1461	// shutdown, where the outer buffer has already translated, and let
1462	// the pass-through below deliver this request untouched.
1463	if ( self::translation_plugin_active() ) {
1464	self::$deferred_key = $key;
1465	// Reaching here means finalize_buffer() ran to completion: the
1466	// status gate passed, should_cache() said yes, and PHP handed us
1467	// the whole buffer. A wp_die() or exit() mid-render unwinds the
1468	// buffer stack WITHOUT calling this callback, so the flag stays
1469	// false and the shutdown writer declines — see the guard there.
1470	self::$render_completed = true;
1471	// A PHP shutdown function, not a WP `shutdown` action: this must
1472	// run after the output-buffer stack has unwound, and WP's
1473	// shutdown action fires while our outer buffer is still open.
1474	register_shutdown_function( array( __CLASS__, 'write_deferred_translated_cache' ) );
1475	return $buffer;
1476	}
1477
1478	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents -- WP_Filesystem requires admin context for credentials; cache writes happen on frontend requests where it's unavailable.
1479	file_put_contents( $file, $full, LOCK_EX );
1480
1481	/**
1482	* Fires after the flat hash cache file ({md5}.html) is written.
1483	*
1484	* Mirror of `xspeed_static_file_written` for the flat cache. The PHP
1485	* serve path (Cache::maybe_serve_brotli / the drop-in) serves THIS
1486	* file and looks for a `{md5}.html.br` sibling — which only the Pro
1487	* Brotli listener on this hook writes. Without it the .br sibling was
1488	* never created and the PHP path could never serve Brotli (FBS-83039,
1489	* Blocker 2): the static-tree .br (written on xspeed_static_file_written)
1490	* lives in a different cache layout the PHP path never reads.
1491	*
1492	* @param string $file Absolute path to the flat cache file just written.
1493	* @param string $full The HTML written to it.
1494	*/
1495	do_action( 'xspeed_flat_file_written', $file, $full );
1496
1497	// Persist a non-default Content-Type so the HIT path can replay it
1498	// (cached feeds must serve application/rss+xml, not text/html).
1499	// Only written when the response set a content-type other than
1500	// the HTML default — pages don't pay for an extra file.
1501	self::write_meta( $key );
1502
1503	// Static-cache tree (xspeed-static/{host}{path}/index.html). The
1504	// .htaccess rewrite block serves this file directly via the web
1505	// server, bypassing PHP for ~3-5× lower TTFB vs the drop-in path.
1506	// store_static() returns silently on any path/permission issue —
1507	// the drop-in remains the safety net.
1508	//
1509	// Skip it entirely when mobile_separate is on: the rewrite is
1510	// disabled in that mode (static_rewrite_allowed()), so a static file
1511	// would only be dead weight — and a device-blind one at that.
1512	// Skip the static-tree write for responses the web server can't replay
1513	// correctly: a non-200 status (a cached 404 would be served as a soft
1514	// 200, FBS-82406) or a non-HTML content-type (a cached feed would go
1515	// out as text/html, FBS-82407). The web server serves these .html files
1516	// directly with no PHP, so there's no .meta replay — keep them on the
1517	// drop-in / PHP path instead, which DOES replay status + content-type.
1518	if ( self::static_rewrite_allowed() && self::response_is_plain_html() ) {
1519	self::store_static( $full );
1520	}
1521
1522	return $buffer;
1523	}
1524
1525	/**
1526	* Write the current response to the static-cache tree at
1527	* `xspeed-static/{host}{request_uri}/index.html`. The web-server
1528	* rewrite block points at this path so cache hits skip PHP
1529	* entirely. Caller already minified/finalized $html.
1530	*
1531	* Path safety: $host is restricted to a `[a-zA-Z0-9.\-]` allowlist;
1532	* $uri has its query string stripped, null bytes removed, '..'
1533	* sequences collapsed, and after concatenation we verify the
1534	* resolved real path stays inside XSPEED_CACHE_STATIC_DIR before
1535	* any write. Anything off the happy path returns silently.
1536	*
1537	* INVARIANT — the static tree is keyed by `{host}{path}` and NOTHING
1538	* else, and both generated rewrites refuse any request that carries a
1539	* query string at all (`RewriteCond %{QUERY_STRING} ^$` on Apache,
1540	* `if ($args)` in nginx_snippet()). So a response may only be stored
1541	* here when cache_key() adds no discriminator beyond `{host}{path}`:
1542	* a query-keyed entry can never be served from here, only mis-served
1543	* as the bare path. Any future opt-in that folds a query param into the
1544	* key needs a guard below, exactly like the search one.
1545	*/
1546	private static function store_static( string $html ): void {
1547	// Search results are keyed by term in cache_key() (`\|s=<term>`) but
1548	// carry the path of whatever URL was searched from — for the usual
1549	// `/?s=<term>` that path is `/`. Writing them here would file the
1550	// results page as `{host}/index.html` and the web server would serve
1551	// it to every visitor as the homepage: an unauthenticated visitor
1552	// poisons the front page with one request. Searches stay on the
1553	// drop-in, which replays the term-keyed entry correctly. (#191)
1554	//
1555	// This is a superset of the query-string check the exclusion gate
1556	// does: it also covers `/?%73=<term>`, which decodes to the same
1557	// search (the shape #109 fixed on the gate side).
1558	if ( self::should_cache_search() ) {
1559	return;
1560	}
1561
1562	$host = isset( $_SERVER['HTTP_HOST'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_HOST'] ) ) : '';
1563	$uri = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '';
1564	$host = preg_replace( '/[^a-zA-Z0-9.\-]/', '', $host );
1565	$uri = str_replace( "\0", '', $uri );
1566	$uri = (string) strtok( $uri, '?' );
1567	if ( '' === $host \|\| '' === $uri ) {
1568	return;
1569	}
1570	// Collapse any traversal sequences before path resolution.
1571	$uri = preg_replace( '#/+#', '/', $uri );
1572	if ( false !== strpos( $uri, '..' ) ) {
1573	return;
1574	}
1575
1576	$base = rtrim( XSPEED_CACHE_STATIC_DIR, '/' );
1577	$dir = $base . '/' . $host . rtrim( $uri, '/' );
1578	$file = $dir . '/index.html';
1579
1580	// Resolve the parent against the cache root to be sure the
1581	// final path is inside our tree even if the OS does anything
1582	// funny with multi-byte sequences.
1583	$base_real = realpath( WP_CONTENT_DIR );
1584	if ( false === $base_real \|\| 0 !== strpos( $base, $base_real ) ) {
1585	return;
1586	}
1587
1588	if ( ! file_exists( $dir ) ) {
1589	wp_mkdir_p( $dir );
1590	}
1591	if ( ! is_dir( $dir ) ) {
1592	return;
1593	}
1594	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents -- Same rationale as the flat-hash cache write above: WP_Filesystem isn't available on frontend requests, and the cache write must happen during shutdown.
1595	$written = file_put_contents( $file, $html, LOCK_EX );
1596
1597	if ( false !== $written ) {
1598	/**
1599	* Fires after a static cache file (index.html) is written.
1600	*
1601	* The extension point for serving pre-compressed siblings:
1602	* the xspeed-pro Brotli module writes `index.html.br` next to
1603	* the file here so the web server's static rewrite can serve a
1604	* Brotli copy to clients that advertise `Accept-Encoding: br`,
1605	* falling back to GZIP / the plain file otherwise. No core
1606	* behavior depends on a listener being present.
1607	*
1608	* @param string $file Absolute path to the static cache file just written.
1609	* @param string $html The HTML written to it.
1610	*/
1611	do_action( 'xspeed_static_file_written', $file, $html );
1612	}
1613	}
1614
1615	/**
1616	* Write the .meta sidecar for a cache entry when the response carries
1617	* anything the HIT path must replay beyond a plain 200 text/html:
1618	* - a non-HTML Content-Type (cached feeds → application/rss+xml,
1619	* sitemaps → text/xml, …), and/or
1620	* - a non-200 status (a cached 404 must serve 404, not 200).
1621	*
1622	* Ordinary 200 text/html pages get NO .meta file, so the common path
1623	* stays a single write.
1624	*
1625	* @param string $key Cache key for the current request.
1626	*/
1627	/**
1628	* True only for a plain 200 text/html response — the only kind the
1629	* web-server static tree can serve correctly (it streams the .html with
1630	* no PHP, so it can't replay a 404 status or a feed Content-Type). Used
1631	* to gate store_static() so cached 404s / feeds stay on the replay-capable
1632	* drop-in / PHP path. (FBS-82406, FBS-82407)
1633	*/
1634	private static function response_is_plain_html(): bool {
1635	$status = function_exists( 'http_response_code' ) ? (int) http_response_code() : 200;
1636	if ( 200 !== $status && $status > 0 ) {
1637	return false;
1638	}
1639	foreach ( headers_list() as $header ) {
1640	if ( 0 === stripos( $header, 'content-type:' ) ) {
1641	$ct = trim( substr( $header, strlen( 'content-type:' ) ) );
1642	if ( '' !== $ct && false === stripos( $ct, 'text/html' ) ) {
1643	return false;
1644	}
1645	}
1646	}
1647	return true;
1648	}
1649
1650	private static function write_meta( string $key ): void {
1651	$content_type = '';
1652	foreach ( headers_list() as $header ) {
1653	if ( 0 === stripos( $header, 'content-type:' ) ) {
1654	$content_type = trim( substr( $header, strlen( 'content-type:' ) ) );
1655	}
1656	}
1657	$status = function_exists( 'http_response_code' ) ? (int) http_response_code() : 200;
1658
1659	$meta = array();
1660	$is_default_type = ( '' === $content_type \|\| false !== stripos( $content_type, 'text/html' ) );
1661	if ( ! $is_default_type ) {
1662	$meta['content_type'] = $content_type;
1663	}
1664	if ( 200 !== $status && $status > 0 ) {
1665	$meta['status'] = $status;
1666	}
1667
1668	// Per-content TTL (seconds). The drop-in and static fast paths can't
1669	// call is_expired() / the xspeed_cache_max_age filter (they run before
1670	// WP), so persist the resolved max-age here whenever it differs from
1671	// the plain page TTL — e.g. the Pro feed cache's 12h vs the 24h page
1672	// default. The fast paths read this to expire correctly. (FBS-82407)
1673	$opts = Settings_Manager::get( 'cache' );
1674	$default_ttl = (int) $opts['cache_expiry'] * HOUR_IN_SECONDS;
1675	$ttl = (int) apply_filters( 'xspeed_cache_max_age', $default_ttl );
1676	if ( $ttl > 0 && $ttl !== $default_ttl ) {
1677	$meta['ttl'] = $ttl;
1678	}
1679
1680	// Nothing to replay → no sidecar.
1681	if ( empty( $meta ) ) {
1682	return;
1683	}
1684
1685	$payload = wp_json_encode( $meta );
1686	if ( false === $payload ) {
1687	return;
1688	}
1689	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents -- our own cache dir; WP_Filesystem needs admin creds unavailable on a frontend shutdown write.
1690	file_put_contents( self::cache_meta_for( $key ), $payload, LOCK_EX );
1691	}
1692
1693	/**
1694	* @param string $cause Free-form human reason. Recorded in the
1695	* Activity log to give users context (e.g.
1696	* 'post saved', 'settings change', 'manual',
1697	* 'theme switch').
1698	*/
1699	/**
1700	* Purge the cache entries for ONE URL — every variant of it: the
1701	* flat-hash entry (+ .meta / .html.br siblings), both device buckets
1702	* (mobile_separate keys them separately), both trailing-slash forms,
1703	* and the static-tree index.html (+ .br) the server rewrite serves.
1704	* The rest of the cache is untouched — this is the surgical
1705	* alternative to purge_all for "I just edited this one page".
1706	*
1707	* @param string $url Absolute URL, or site-relative path ("/about/").
1708	* @param string $cause Who asked, for the purge log. See purge_all().
1709	* @return int Number of cache files removed.
1710	*/
1711	public static function purge_url( string $url, string $cause = 'manual' ): int {
1712	$parts = function_exists( 'wp_parse_url' ) ? wp_parse_url( $url ) : parse_url( $url ); // phpcs:ignore WordPress.WP.AlternativeFunctions.parse_url_parse_url -- fallback for early-boot contexts only.
1713	if ( ! is_array( $parts ) ) {
1714	return 0;
1715	}
1716	$host = isset( $parts['host'] ) ? strtolower( (string) $parts['host'] ) : '';
1717	if ( '' === $host && function_exists( 'home_url' ) ) {
1718	$home = function_exists( 'wp_parse_url' ) ? wp_parse_url( home_url( '/' ) ) : parse_url( home_url( '/' ) ); // phpcs:ignore WordPress.WP.AlternativeFunctions.parse_url_parse_url -- see above.
1719	$host = is_array( $home ) && isset( $home['host'] ) ? strtolower( (string) $home['host'] ) : '';
1720	}
1721	if ( '' === $host ) {
1722	return 0;
1723	}
1724	$path = isset( $parts['path'] ) ? (string) $parts['path'] : '/';
1725	$path = '/' . ltrim( $path, '/' );
1726	if ( false !== strpos( $path, '..' ) ) {
1727	return 0;
1728	}
1729
1730	// The cache key preserves REQUEST_URI's trailing-slash form, so
1731	// purge both. Root stays a single '/'.
1732	$forms = array( $path );
1733	if ( '/' !== $path ) {
1734	$forms[] = rtrim( $path, '/' );
1735	$forms[] = rtrim( $path, '/' ) . '/';
1736	}
1737	$forms = array_unique( $forms );
1738
1739	/*
1740	* Entries live under the bucket they were written for, and this URL's
1741	* site may not be the one serving THIS request (a cross-site purge on
1742	* multisite, WP-CLI, or cron). Build the directory from the URL's own
1743	* host AND path. (#6)
1744	*
1745	* Host alone is wrong on a subdirectory network: `store()` wrote to
1746	* `<host>/<prefix>/`, so looking in `<host>/` found nothing and the
1747	* call reported "already cold" while the page kept serving HIT — a
1748	* false success, which is worse than an error. The prefix has to come
1749	* from the URL being purged rather than from the current blog, because
1750	* the caller is usually purging some OTHER site. (QA B2 on #166)
1751	*/
1752	$base = XSPEED_CACHE_DIR . '/' . self::bucket_for_url( $host, $path );
1753
1754	$count = 0;
1755	foreach ( $forms as $uri ) {
1756	// '' = mobile_separate off; '\|m' / '\|d' = the device buckets.
1757	foreach ( array( '', '\|m', '\|d' ) as $device ) {
1758	$key = md5( $host . $uri . $device );
1759	$file = $base . '/' . $key . '.html';
1760	if ( is_file( $file ) ) {
1761	wp_delete_file( $file );
1762	++$count;
1763	}
1764	foreach ( array( $base . '/' . $key . '.meta', $file . '.br' ) as $sidecar ) {
1765	if ( is_file( $sidecar ) ) {
1766	wp_delete_file( $sidecar );
1767	}
1768	}
1769	}
1770	}
1771
1772	// Static tree (served directly by the nginx/.htaccess rewrite).
1773	if ( defined( 'XSPEED_CACHE_STATIC_DIR' ) ) {
1774	$dir = rtrim( XSPEED_CACHE_STATIC_DIR, '/' ) . '/' . $host . ( '/' === $path ? '' : rtrim( $path, '/' ) );
1775	$file = $dir . '/index.html';
1776	if ( is_file( $file ) ) {
1777	wp_delete_file( $file );
1778	++$count;
1779	}
1780	if ( is_file( $file . '.br' ) ) {
1781	wp_delete_file( $file . '.br' );
1782	}
1783	}
1784
1785	if ( $count > 0 ) {
1786	Cache_Inventory::invalidate();
1787	Activity_Log::record(
1788	'cache_purge_url',
1789	sprintf(
1790	/* translators: 1: cause of the purge, 2: URL or path, 3: number of files removed. */
1791	__( 'Purged one URL (%1$s) — %2$s, %3$d file(s) removed', 'xspeed' ),
1792	$cause,
1793	$host . $path,
1794	$count
1795	),
1796	Activity_Log::INFO
1797	);
1798	}
1799
1800	return $count;
1801	}
1802
1803	/**
1804	* Purge this site's cache.
1805	*
1806	* On multisite every blog shares one cache directory, so an unscoped
1807	* sweep here took the whole network cold — one subsite's settings save
1808	* or post publish rebuilt every other site from PHP. Entries are stored
1809	* per host (see host_dir()), and the sweep is scoped to match, so a
1810	* purge originating on site-a leaves site-b's cache warm. (#6)
1811	*
1812	* @param string $cause Who asked, for the purge log.
1813	* @param string\|null $host Host to purge. Defaults to the current site.
1814	* Pass '*' to sweep the ENTIRE tree — network
1815	* admin's "purge all sites", and the migration
1816	* of pre-#6 entries that sit in the tree root.
1817	*/
1818	public static function purge_all( string $cause = 'manual', ?string $host = null ) {
1819	$network_wide = ( '*' === $host );
1820	// The flat tree buckets by a flattened segment (host/a-b) while the
1821	// static tree mirrors the URL (host/a/b), so they need separate
1822	// scopes — see current_host_dir() vs current_static_scope().
1823	$static_scope = '';
1824	if ( null === $host \|\| $network_wide ) {
1825	$scope = $network_wide ? '' : self::current_host_dir();
1826	$static_scope = $network_wide ? '' : self::current_static_scope();
1827	} else {
1828	$dir = self::host_dir( $host );
1829	$scope = '' === $dir ? 'default' : $dir;
1830	$static_scope = $scope;
1831	}
1832
1833	$count = 0;
1834	if ( is_dir( XSPEED_CACHE_DIR ) ) {
1835	// Scoped to one host directory, or the whole tree (including the
1836	// legacy top-level entries written before #6) when network-wide.
1837	/*
1838	* Network-wide sweeps go TWO levels deep, not one. A subdirectory
1839	* subsite's bucket is `<host>/<prefix>/`, so globbing only
1840	* `<cache>/*` reached the main site and left every subsite's
1841	* entries in place. (QA D5 on #166)
1842	*
1843	* A scoped purge also has to cover its own nested buckets: when
1844	* the main blog of a subdirectory network purges, `<host>/` is its
1845	* bucket and `<host>/one/` belongs to another blog — so the scoped
1846	* branch deliberately does NOT descend, which is what keeps
1847	* site-level purges isolated.
1848	*/
1849	$roots = $network_wide
1850	? array_merge(
1851	array( XSPEED_CACHE_DIR ),
1852	array_filter( (array) glob( XSPEED_CACHE_DIR . '/*', GLOB_ONLYDIR ) ),
1853	array_filter( (array) glob( XSPEED_CACHE_DIR . '//', GLOB_ONLYDIR ) )
1854	)
1855	: array( XSPEED_CACHE_DIR . '/' . $scope );
1856
1857	foreach ( $roots as $root ) {
1858	/*
1859	* min/ and rest/ are swept by their own purgers below; never
1860	* treat them as host buckets.
1861	*
1862	* Checked on every path SEGMENT, not just the basename: now
1863	* that the network-wide glob descends two levels it can reach
1864	* `min/combined`, whose basename is `combined` and would sail
1865	* past a basename-only test — deleting the combined
1866	* stylesheets out from under the pages that link them.
1867	*/
1868	if ( ! $network_wide \|\| XSPEED_CACHE_DIR !== $root ) {
1869	$relative = trim( str_replace( XSPEED_CACHE_DIR, '', (string) $root ), '/' );
1870	$segments = '' === $relative ? array() : explode( '/', $relative );
1871	if ( array_intersect( $segments, array( 'min', 'rest' ) ) ) {
1872	continue;
1873	}
1874	}
1875	if ( ! is_dir( $root ) ) {
1876	continue;
1877	}
1878	$files = glob( $root . '/*.html' );
1879	if ( $files ) {
1880	$count += count( $files );
1881	foreach ( $files as $f ) {
1882	wp_delete_file( $f );
1883	}
1884	}
1885	// Remove the .meta sidecars (content-type for feeds/sitemaps)
1886	// alongside their .html entries. Not counted — they're not
1887	// cache "pages", just per-entry metadata.
1888	$meta = glob( $root . '/*.meta' );
1889	if ( $meta ) {
1890	foreach ( $meta as $m ) {
1891	wp_delete_file( $m );
1892	}
1893	}
1894	// Remove precompressed siblings (e.g. <key>.html.br from the Pro
1895	// Brotli module). Not counted — same as .meta. Without this a
1896	// purge leaves stale .br bodies behind: disk bloat, and a
1897	// staleness window if precompression is later disabled.
1898	$br = glob( $root . '/*.br' );
1899	if ( $br ) {
1900	foreach ( $br as $b ) {
1901	wp_delete_file( $b );
1902	}
1903	}
1904	}
1905	}
1906	// Static-cache tree purge — recursive because the layout is
1907	// xspeed-static/{host}/{path}/index.html, so a flat glob can't
1908	// reach everything. Already host-segmented, so scoping is just a
1909	// matter of starting one level down.
1910	if ( is_dir( XSPEED_CACHE_STATIC_DIR ) ) {
1911	$static_root = $network_wide
1912	? XSPEED_CACHE_STATIC_DIR
1913	: XSPEED_CACHE_STATIC_DIR . '/' . $static_scope;
1914	if ( is_dir( $static_root ) ) {
1915	$count += self::rmtree_html( $static_root );
1916	}
1917	}
1918	// REST response cache (cache/xspeed/rest/*.json) — same purge
1919	// triggers (publish, settings change) invalidate it too.
1920	$count += Rest_Cache::purge();
1921
1922	// Minified + combined CSS/JS (cache/xspeed/min/ and min/combined/).
1923	// purge_all is a full filesystem sweep and must clear these too, even
1924	// when the Minify module is currently disabled — orphaned min/ files
1925	// from a feature the user later turned off must still be removed, and
1926	// a stale combined-<hash>.css that the regenerated page no longer
1927	// references otherwise 404s and breaks the frontend. (FBS-83114/83116)
1928	if ( class_exists( '\\XSpeed\\Minifier' ) ) {
1929	Minifier::purge_minified();
1930	}
1931
1932	// Persistent object cache (Redis / Memcached). Flush regardless of
1933	// whether the Object Cache module is currently enabled — a drop-in
1934	// installed earlier keeps serving until flushed.
1935	//
1936	// wp_cache_flush() is NETWORK-global: on multisite it would drop
1937	// every other site's object cache too, which is the same bug this
1938	// change fixes for the page cache. Prefer the blog-scoped flush
1939	// (WP 6.1+) unless we were explicitly asked to go network-wide. (#6)
1940	if ( ! $network_wide && is_multisite() && function_exists( 'wp_cache_flush_group' ) && function_exists( 'wp_cache_supports' ) && wp_cache_supports( 'flush_group' ) ) {
1941	// Blog-scoped groups only; a shared/global group (site options,
1942	// user meta) is intentionally left alone.
1943	foreach ( array( 'options', 'posts', 'terms', 'post_meta', 'comment' ) as $group ) {
1944	wp_cache_flush_group( $group );
1945	}
1946	} elseif ( function_exists( 'wp_cache_flush' ) ) {
1947	wp_cache_flush();
1948	}
1949
1950	self::update_stats( array( 'last_purge' => time() ) );
1951
1952	// Fire AFTER the local sweep so module listeners (Critical CSS,
1953	// Unused CSS, Cloudflare edge purge) run — this action had three
1954	// registered listeners but was never emitted. Treat it as additive
1955	// (CDN / edge invalidation), not the mechanism for clearing local
1956	// files. (FBS-83114)
1957	do_action( 'xspeed_after_purge_all', $cause );
1958
1959	// The list behind the "Cached pages" card is memoized for a minute;
1960	// a purge has to drop it or the drill-down shows pages that no
1961	// longer exist.
1962	Cache_Inventory::invalidate();
1963
1964	// Trigger of WP_CLI / hook / admin-bar purges all hit the same
1965	// path. Record once with the supplied cause so the dashboard
1966	// activity feed reads naturally.
1967	Activity_Log::record(
1968	'cache_purged',
1969	sprintf( 'Cache purged (%s) — %d file%s removed', $cause, $count, 1 === $count ? '' : 's' ),
1970	Activity_Log::INFO
1971	);
1972
1973	return $count;
1974	}
1975
1976	/**
1977	* The per-type purge menu, LiteSpeed-style. Each entry is a cache type
1978	* the user can purge individually from the admin-bar dropdown. `visible`
1979	* controls whether the item shows (active + licensed module only) — it
1980	* NEVER limits Purge All, which always sweeps everything on disk.
1981	*
1982	* Pro registers its own types (Critical CSS, Unused CSS, …) by filtering
1983	* `xspeed_purge_types`, so Free degrades gracefully when Pro is absent.
1984	*
1985	* @return array<string,array{label:string,visible:bool}>
1986	*/
1987	public static function purge_types(): array {
1988	$minify_on = false;
1989	if ( class_exists( '\\XSpeed\\Settings_Manager' ) ) {
1990	$min = Settings_Manager::get( 'minify' );
1991	$minify_on = ! empty( $min['minify_css'] ) \|\| ! empty( $min['minify_js'] ) \|\| ! empty( $min['combine_css'] ) \|\| ! empty( $min['combine_js'] );
1992	}
1993	// Object cache is "active" when an external object-cache drop-in is in
1994	// use — the canonical WP signal, independent of our settings option.
1995	$oc_on = function_exists( 'wp_using_ext_object_cache' ) && wp_using_ext_object_cache();
1996
1997	$types = array(
1998	'all' => array(
1999	'label' => __( 'Purge All', 'xspeed' ),
2000	'visible' => true,
2001	),
2002	'page' => array(
2003	'label' => __( 'Purge Page / Static Cache', 'xspeed' ),
2004	'visible' => true,
2005	),
2006	'assets' => array(
2007	'label' => __( 'Purge CSS / JS Cache', 'xspeed' ),
2008	'visible' => $minify_on,
2009	),
2010	'object' => array(
2011	'label' => __( 'Purge Object Cache', 'xspeed' ),
2012	'visible' => $oc_on,
2013	),
2014	'rest' => array(
2015	'label' => __( 'Purge REST Cache', 'xspeed' ),
2016	'visible' => true,
2017	),
2018	);
2019
2020	/**
2021	* Filter the admin-bar purge-type menu. Pro modules add their own
2022	* (Critical CSS, Unused CSS, CDN). Adding a type here only adds a
2023	* MENU item — purge_type() must know how to handle the same slug.
2024	*
2025	* @param array $types Map of slug => [label, visible].
2026	*/
2027	return (array) apply_filters( 'xspeed_purge_types', $types );
2028	}
2029
2030	/**
2031	* Purge a single cache type by slug. 'all' delegates to purge_all();
2032	* every other slug clears just its own artifacts. Unknown slugs (e.g. a
2033	* Pro type) fan out via the `xspeed_purge_type_{slug}` action so the
2034	* owning module can handle it. Returns the number of items removed where
2035	* countable.
2036	*
2037	* @param string $type Cache type slug.
2038	* @param string $cause Who asked. Threaded through so the purge log can
2039	* tell an AI assistant's purge apart from a click —
2040	* "the cache cleared four times today" is only
2041	* actionable once you know what kept clearing it.
2042	*/
2043	public static function purge_type( string $type, string $cause = 'manual' ): int {
2044	switch ( $type ) {
2045	case 'all':
2046	return self::purge_all( $cause );
2047
2048	case 'page':
2049	$count = self::purge_pages();
2050	self::update_stats( array( 'last_purge' => time() ) );
2051	Cache_Inventory::invalidate();
2052	self::record_partial_purge( 'page', $cause, $count );
2053	return $count;
2054
2055	case 'assets':
2056	if ( class_exists( '\\XSpeed\\Minifier' ) ) {
2057	Minifier::purge_minified();
2058	}
2059	// Deleting min/ without clearing the pages that link it left
2060	// every cached page pointing at files that no longer exist.
2061	// WordPress answers the missing asset by 301-ing to its
2062	// pretty-permalink form and serving the 404 TEMPLATE as
2063	// `HTTP 200 text/html`, which the browser accepts as a
2064	// stylesheet and parses to zero rules — no console error, no
2065	// network failure, no 4xx anywhere in devtools. The pages
2066	// stayed broken for the rest of the TTL (7 days on
2067	// Aggressive, up to 30), and the admin who clicked could not
2068	// see it: they are logged in, so their own requests bypass
2069	// the page cache and re-render, regenerating the assets as a
2070	// side effect. Only anonymous visitors were served the stale
2071	// HTML. (#244)
2072	//
2073	// The assets are the pages' dependency, so invalidating them
2074	// invalidates the pages. Same invariant Cache_GC enforces
2075	// with is_referenced(): never leave a cached page pointing at
2076	// an asset that is gone.
2077	$count = self::purge_pages();
2078	self::update_stats( array( 'last_purge' => time() ) );
2079	Cache_Inventory::invalidate();
2080	self::record_partial_purge( 'assets', $cause, $count );
2081	return $count;
2082
2083	case 'object':
2084	if ( function_exists( 'wp_cache_flush' ) ) {
2085	wp_cache_flush();
2086	}
2087	self::record_partial_purge( 'object cache', $cause, null );
2088	return 0;
2089
2090	case 'rest':
2091	$count = Rest_Cache::purge();
2092	self::record_partial_purge( 'REST responses', $cause, $count );
2093	return $count;
2094
2095	default:
2096	return self::purge_type_unhandled( $type, $cause );
2097	}
2098	}
2099
2100	/**
2101	* Delete this site's cached pages from both the flat and static trees.
2102	*
2103	* Extracted so the `assets` purge can reuse it: minified assets are a
2104	* dependency of the cached HTML, so clearing them must clear the pages
2105	* too or the pages are left referencing deleted files (#244).
2106	*
2107	* @return int Number of page entries removed.
2108	*/
2109	private static function purge_pages(): int {
2110	$count = 0;
2111	// Scoped to this site — see purge_all(). (#6)
2112	$scope = self::current_host_dir();
2113	$flat_root = XSPEED_CACHE_DIR . '/' . $scope;
2114	if ( is_dir( $flat_root ) ) {
2115	foreach ( (array) glob( $flat_root . '/*.html' ) as $f ) {
2116	wp_delete_file( $f );
2117	++$count;
2118	}
2119	foreach ( (array) glob( $flat_root . '/*.meta' ) as $m ) {
2120	wp_delete_file( $m );
2121	}
2122	foreach ( (array) glob( $flat_root . '/*.br' ) as $b ) {
2123	wp_delete_file( $b );
2124	}
2125	}
2126	$static_root = XSPEED_CACHE_STATIC_DIR . '/' . self::current_static_scope();
2127	if ( is_dir( $static_root ) ) {
2128	$count += self::rmtree_html( $static_root );
2129	}
2130
2131	return $count;
2132	}
2133
2134	/**
2135	* A purge type this class does not own — a Pro or third-party module
2136	* registered it via the `xspeed_purge_types` filter, so hand it off.
2137	*
2138	* @param string $type Purge-type slug.
2139	* @param string $cause Who asked.
2140	*/
2141	private static function purge_type_unhandled( string $type, string $cause ): int {
2142	do_action( 'xspeed_purge_type_' . $type );
2143	self::record_partial_purge( $type, $cause, null );
2144
2145	return 0;
2146	}
2147
2148	/**
2149	* Log a partial purge so the drill-down behind "Last purge" shows every
2150	* clear, not only the full ones. Without this a site whose object cache
2151	* is flushed on a schedule looks, from the log, like nothing happens.
2152	*
2153	* @param string $what Human label for the slice purged.
2154	* @param string $cause Who asked.
2155	* @param int\|null $count Items removed, when countable.
2156	*/
2157	private static function record_partial_purge( string $what, string $cause, ?int $count ): void {
2158	$message = null === $count
2159	? sprintf(
2160	/* translators: 1: what was purged, 2: cause of the purge. */
2161	__( 'Purged %1$s (%2$s)', 'xspeed' ),
2162	$what,
2163	$cause
2164	)
2165	: sprintf(
2166	/* translators: 1: what was purged, 2: cause of the purge, 3: number of files removed. */
2167	__( 'Purged %1$s (%2$s) — %3$d file(s) removed', 'xspeed' ),
2168	$what,
2169	$cause,
2170	$count
2171	);
2172
2173	Activity_Log::record( 'cache_purged', $message, Activity_Log::INFO );
2174	}
2175
2176	/**
2177	* Clear the static tree only, leaving the flat cache in place.
2178	*
2179	* A narrower purge_all() for the case where only the web-server tree can
2180	* be wrong: its files are keyed by `{host}{path}` and nothing else, so a
2181	* response filed under the wrong path poisons it while the flat cache —
2182	* keyed by cache_key(), discriminators included — stays correct. Avoids
2183	* throwing away Critical CSS, minified bundles and the object cache to
2184	* fix a static-only problem.
2185	*
2186	* @return int Number of index.html files removed.
2187	*/
2188	public static function purge_static_tree(): int {
2189	return self::rmtree_html( XSPEED_CACHE_STATIC_DIR );
2190	}
2191
2192	/**
2193	* Recursively delete every `index.html` (and its precompressed
2194	* `index.html.br` sibling, if the Pro Brotli module wrote one) plus
2195	* empty directories inside the static-cache tree. Used by purge_all().
2196	* Returns the number of .html files removed so purge stats stay accurate
2197	* across the flat + static caches — .br siblings are not counted
2198	* (they're encodings of a page, not pages).
2199	*/
2200	private static function rmtree_html( string $dir ): int {
2201	if ( ! is_dir( $dir ) ) {
2202	return 0;
2203	}
2204	$removed = 0;
2205	// SCANDIR_SORT_NONE skips alphabetic sort — we're going to walk
2206	// the whole tree regardless of order.
2207	$entries = @scandir( $dir, SCANDIR_SORT_NONE ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
2208	if ( false === $entries ) {
2209	return 0;
2210	}
2211	foreach ( $entries as $entry ) {
2212	if ( '.' === $entry \|\| '..' === $entry ) {
2213	continue;
2214	}
2215	$path = $dir . '/' . $entry;
2216	if ( is_dir( $path ) ) {
2217	$removed += self::rmtree_html( $path );
2218	// Best-effort empty-dir cleanup; ignore failures (a
2219	// foreign file inside would block rmdir, which is fine).
2220	// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged, WordPress.WP.AlternativeFunctions.file_system_operations_rmdir -- Best-effort empty-dir cleanup; WP_Filesystem needs admin credentials we don't have during a normal purge.
2221	@rmdir( $path );
2222	continue;
2223	}
2224	if ( substr( $entry, -5 ) === '.html' ) {
2225	wp_delete_file( $path );
2226	++$removed;
2227	} elseif ( substr( $entry, -3 ) === '.br' ) {
2228	// Precompressed sibling (index.html.br). Remove it too so a
2229	// purge doesn't orphan stale Brotli bodies. Not counted.
2230	wp_delete_file( $path );
2231	}
2232	}
2233	return $removed;
2234	}
2235
2236	/**
2237	* Drop a "silence is golden" index.php into a directory so apaches/nginx
2238	* with directory listing enabled don't expose cache contents.
2239	*/
2240	public static function write_silence( $dir ) {
2241	$file = trailingslashit( $dir ) . 'index.php';
2242	if ( ! file_exists( $file ) ) {
2243	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents -- WP_Filesystem requires admin context for credentials; cache dir setup may run during a frontend page render.
2244	file_put_contents( $file, "<?php\n// Silence is golden.\n" );
2245	}
2246	}
2247
2248	/**
2249	* The raw xspeed_stats option as an array. Keys currently in use:
2250	* 'last_purge', 'last_gc', 'gc_removed', 'gc_removed_total'.
2251	*/
2252	public static function get_stats_option(): array {
2253	$stats = get_option( 'xspeed_stats', array() );
2254	return is_array( $stats ) ? $stats : array();
2255	}
2256
2257	/**
2258	* Persist stats with autoload disabled — stats are only read in admin
2259	* contexts, so there is no reason to inflate every frontend request's
2260	* `wp_load_alloptions()` payload.
2261	*
2262	* MERGES into whatever is already stored. It used to overwrite, which
2263	* was harmless while `last_purge` was the only key — with the GC keys
2264	* alongside it, a purge would have wiped the GC history and vice versa.
2265	*/
2266	public static function update_stats( array $stats ) {
2267	if ( false === get_option( 'xspeed_stats', false ) ) {
2268	add_option( 'xspeed_stats', $stats, '', 'no' );
2269	return;
2270	}
2271	update_option( 'xspeed_stats', array_merge( self::get_stats_option(), $stats ) );
2272	}
2273
2274	public static function get_stats() {
2275	$count = 0;
2276	$size = 0;
2277	// This site's entries only — on multisite the tree is shared, so an
2278	// unscoped count reported the whole network's pages on every
2279	// subsite's dashboard. (#6)
2280	$flat_root = XSPEED_CACHE_DIR . '/' . self::current_host_dir();
2281	if ( is_dir( $flat_root ) ) {
2282	$files = glob( $flat_root . '/*.html' );
2283	if ( $files ) {
2284	$count = count( $files );
2285	foreach ( $files as $f ) {
2286	$size += filesize( $f );
2287	}
2288	}
2289	}
2290	// Drain the HIT-log file BEFORE reading totals. Two serve paths that
2291	// bypass the normal in-PHP record_hit() append one line per HIT here:
2292	// the nginx server-level rewrite (see nginx_snippet(), never reaches
2293	// PHP) and the advanced-cache.php drop-in (runs pre-WordPress, can't
2294	// reach Hit_Counter). Without this drain both look like a 0% hit-ratio
2295	// on a perfectly working cache.
2296	Hit_Counter::collect_nginx_log_hits();
2297
2298	// Apache/LiteSpeed static-rewrite HITs are served straight from disk
2299	// by .htaccess and never reach PHP either — but there's no .htaccess
2300	// equivalent of nginx's access_log directive, so we count them by
2301	// scanning the web server's own access log incrementally. No-op when
2302	// the log isn't readable (managed hosts) — see the method docblock.
2303	Hit_Counter::collect_server_log_hits();
2304
2305	$stats = get_option( 'xspeed_stats', array() );
2306	$totals = Hit_Counter::totals_24h();
2307	return array(
2308	'cached_pages' => $count,
2309	'cache_size' => $size,
2310	'last_purge' => isset( $stats['last_purge'] ) ? (int) $stats['last_purge'] : 0,
2311	// Rolling 24h cache performance — sourced from Hit_Counter's
2312	// hourly buckets. The frontend uses hit_ratio to drive the
2313	// CacheHero stat grid + the Health module's panel.
2314	'hits_24h' => $totals['hits'],
2315	'misses_24h' => $totals['misses'],
2316	'hit_ratio' => $totals['ratio'],
2317	// Requests kept OUT of the ratio (404s + bots) — surfaced as its own
2318	// "absorbed N scanner/bot requests" line rather than distorting the
2319	// cache-performance number. (#118)
2320	'excluded_24h' => $totals['excluded'],
2321	// True when an edge cache (Cloudflare) fronts the origin, so hits are
2322	// absorbed before reaching PHP. The dashboard labels the ratio
2323	// "origin-layer only" instead of implying it's the full picture. (#118)
2324	'edge_cache' => self::edge_cache_detected(),
2325	);
2326	}
2327
2328	/**
2329	* Whether the current request should be kept OUT of the cache hit/miss
2330	* ratio: a genuine 404, or a known bot / scanner. Runs at template_redirect
2331	* time, so is_404() is resolved. (#118)
2332	*/
2333	private static function miss_is_excluded(): bool {
2334	if ( function_exists( 'is_404' ) && is_404() ) {
2335	return true;
2336	}
2337	$ua = isset( $_SERVER['HTTP_USER_AGENT'] )
2338	? sanitize_text_field( wp_unslash( (string) $_SERVER['HTTP_USER_AGENT'] ) )
2339	: '';
2340	return Hit_Counter::is_bot_ua( $ua );
2341	}
2342
2343	/**
2344	* Whether an edge cache fronts this origin. Today: the Cloudflare
2345	* integration is connected — so an unknown share of hits is served at the
2346	* edge and never counted here, making the origin ratio a partial view the
2347	* dashboard must label as such. (#118)
2348	*/
2349	private static function edge_cache_detected(): bool {
2350	$cf = get_option( 'xspeed_module_cloudflare', array() );
2351	return is_array( $cf ) && ! empty( $cf['enabled'] );
2352	}
2353
2354	/**
2355	* Apply the user's enable/disable choice. Called from the REST toggle
2356	* endpoint, which is gated by current_user_can( 'manage_options' ) and
2357	* a verified REST nonce.
2358	*
2359	* This is the only path that ENABLES caching — a drop-in is never
2360	* created for a user who hasn't opted in, which is the guideline that
2361	* matters (a plugin must not install drop-ins or edit wp-config.php
2362	* on a fresh activation). RESTORING the drop-in for a site that
2363	* already has cache_enabled = true is a different act and is handled
2364	* by restore_dropin_if_enabled() on activation and auto_heal() at
2365	* runtime; without it every plugin update silently un-caches the site.
2366	*
2367	* @param bool $enable User's choice.
2368	* @return array{
2369	* enabled: bool,
2370	* dropin_installed: bool,
2371	* wp_cache_constant: bool,
2372	* wp_config_writable: bool,
2373	* manual_snippet: ?string
2374	* }
2375	*/
2376	public static function toggle( $enable ) {
2377	$enable = (bool) $enable;
2378
2379	if ( $enable ) {
2380	$dropin_ok = self::install_dropin();
2381	$wp_config_ok = self::set_wp_cache_constant( true );
2382	$rewrite_ok = self::install_rewrite();
2383	self::ensure_hits_log_file();
2384	self::sync_mobile_flag();
2385	$snippet = $wp_config_ok ? null : "define( 'WP_CACHE', true );";
2386
2387	Activity_Log::record(
2388	'cache_enabled_event',
2389	$wp_config_ok
2390	? 'Cache enabled. Drop-in installed, WP_CACHE constant set.'
2391	: 'Cache enabled. Drop-in installed; wp-config.php not writable — add the WP_CACHE snippet manually.',
2392	$wp_config_ok ? Activity_Log::SUCCESS : Activity_Log::WARN
2393	);
2394
2395	return array(
2396	'enabled' => true,
2397	'dropin_installed' => (bool) $dropin_ok,
2398	'wp_cache_constant' => (bool) $wp_config_ok,
2399	'rewrite_installed' => (bool) $rewrite_ok,
2400	'wp_config_writable' => self::wp_config_writable(),
2401	'manual_snippet' => $snippet,
2402	'nginx_snippet' => self::nginx_snippet(),
2403	// Unified server-block snippet aggregating every enabled
2404	// module's directives — the same value the dashboard and
2405	// Health insight render. The wizard shows this so all three
2406	// surfaces stay in lockstep. Null on non-nginx hosts.
2407	'nginx_server_block' => self::full_nginx_server_block(),
2408	);
2409	}
2410
2411	self::remove_dropin();
2412	self::set_wp_cache_constant( false );
2413	self::remove_rewrite();
2414	// Drop the device-bucket marker too — with the drop-in gone there's
2415	// nothing left to read it, and leaving it behind would dirty a fresh
2416	// re-enable (and leaks across test runs).
2417	self::sync_mobile_flag( false );
2418
2419	Activity_Log::record(
2420	'cache_disabled_event',
2421	'Cache disabled. Drop-in removed.',
2422	Activity_Log::INFO
2423	);
2424
2425	return array(
2426	'enabled' => false,
2427	'dropin_installed' => false,
2428	'wp_cache_constant' => false,
2429	'rewrite_installed' => false,
2430	'wp_config_writable' => self::wp_config_writable(),
2431	'manual_snippet' => null,
2432	'nginx_snippet' => self::nginx_snippet(),
2433	'nginx_server_block' => self::full_nginx_server_block(),
2434	);
2435	}
2436
2437	/**
2438	* Check wp-config.php writability via WP_Filesystem. Plugin Check flags
2439	* direct is_writable() under WordPress.WP.AlternativeFunctions.
2440	*/
2441	private static function wp_config_writable() {
2442	global $wp_filesystem;
2443	if ( ! function_exists( 'WP_Filesystem' ) ) {
2444	require_once ABSPATH . 'wp-admin/includes/file.php';
2445	}
2446	WP_Filesystem();
2447
2448	return $wp_filesystem ? (bool) $wp_filesystem->is_writable( ABSPATH . 'wp-config.php' ) : false;
2449	}
2450
2451	/**
2452	* Nginx server-block snippet mirroring the Apache rewrite block.
2453	* We never auto-write nginx config — it sits outside the WordPress
2454	* root and is owned by the server admin — but the dashboard
2455	* surfaces this snippet when nginx is detected so the admin can
2456	* paste it once and unlock the same PHP-bypass speedup we get on
2457	* Apache / LiteSpeed via .htaccess.
2458	*
2459	* Returns null when the server isn't nginx (no point showing it).
2460	*/
2461	/**
2462	* Create wp-content/cache/xspeed/hits.log as an empty file so the
2463	* server-level rewrite's `access_log` directive has somewhere to
2464	* write on first request. Idempotent — touches an existing file
2465	* without disturbing accumulated lines. Called from Cache::toggle()
2466	* on enable and from auto_heal() when the file is missing.
2467	*
2468	* Permissions matter here. The file is created by PHP-FPM (often uid
2469	* www-data), but the nginx process that appends HIT lines may run as a
2470	* DIFFERENT uid — on multi-container hosts (e.g. xclude/Kinsta: nginx in
2471	* its own container as uid `nginx`, PHP-FPM in another as `www-data`)
2472	* they don't share a user at all. A default-umask 0644 file is then
2473	* unwritable by nginx, the access_log write silently fails, and the
2474	* dashboard shows a 0% hit ratio even though static HITs are serving.
2475	* So we widen the dir to 0777 and the file to 0666 — group/other write —
2476	* so whatever uid nginx runs as can append. (The file holds only HIT
2477	* request lines, no secrets.)
2478	*/
2479	/**
2480	* Directory holding the nginx hit log. Lives under uploads/, NOT the
2481	* cache dir — uninstall.php and a cache purge both delete the cache
2482	* dir, which would orphan the pasted nginx `access_log` directive's
2483	* parent directory and make `nginx -t` fail [emerg], taking down every
2484	* vhost on the host (FBS-82478). uploads/ always exists, isn't a
2485	* plugin-managed cache dir, and is never deleted on uninstall — so the
2486	* directive's target dir survives both, and nginx (which creates a
2487	* missing log FILE but not a missing DIR) can always open it.
2488	*
2489	* Falls back to the cache dir only if uploads is somehow unavailable.
2490	*/
2491	public static function hits_log_dir(): string {
2492	if ( function_exists( 'wp_upload_dir' ) ) {
2493	$uploads = wp_upload_dir( null, false );
2494	if ( is_array( $uploads ) && empty( $uploads['error'] ) && ! empty( $uploads['basedir'] ) ) {
2495	return rtrim( (string) $uploads['basedir'], '/' ) . '/xspeed';
2496	}
2497	}
2498	return XSPEED_CACHE_DIR;
2499	}
2500
2501	/** Absolute path to the nginx hit log file. */
2502	public static function hits_log_path(): string {
2503	return self::hits_log_dir() . '/hits.log';
2504	}
2505
2506	/**
2507	* Sync the drop-in's mobile-bucket flag file with the `mobile_separate`
2508	* setting. The drop-in (advanced-cache.php) runs before WordPress loads,
2509	* so it can't read the option — instead it checks for a zero-byte
2510	* `.mobile-separate` marker next to the cache files. When the setting is
2511	* on we touch the marker; when off we remove it. The drop-in's cache_key
2512	* computation keys off the marker's presence so its '\|m'/'\|d' device
2513	* bucket stays in lockstep with Cache::cache_key().
2514	*
2515	* Without this, turning on mobile_separate made Cache::store() write keys
2516	* with a '\|d'/'\|m' suffix the drop-in never reproduced — so the drop-in's
2517	* file_exists() always missed, every HIT fell through to a full WP boot,
2518	* and the fast pre-WP path was silently dead.
2519	*
2520	* @param bool\|null $enabled Force a state; null reads the current setting.
2521	*/
2522	/**
2523	* Write the subdirectory-multisite path list the drop-in needs to work
2524	* out which blog a request belongs to.
2525	*
2526	* The drop-in runs before WordPress, so it cannot call is_multisite()
2527	* or get_blog_details(). It can only see REQUEST_URI — so we persist the
2528	* network's blog paths (one per line, longest first) next to the cache
2529	* files, exactly as sync_mobile_flag() persists the device flag. The
2530	* drop-in prefix-matches the URI against that list to pick the same
2531	* bucket Cache::current_host_dir() picks. (#6)
2532	*
2533	* No file is written for a single site or a subdomain network — there
2534	* the host alone identifies the blog and the bucket carries no prefix.
2535	*/
2536	public static function sync_site_paths(): void {
2537	$file = XSPEED_CACHE_DIR . '/.site-paths';
2538
2539	$needed = function_exists( 'is_multisite' ) && is_multisite()
2540	&& ( ! function_exists( 'is_subdomain_install' ) \|\| ! is_subdomain_install() );
2541
2542	if ( ! $needed ) {
2543	if ( file_exists( $file ) ) {
2544	// phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink, WordPress.PHP.NoSilencedErrors.Discouraged -- plain marker removal; non-fatal.
2545	@unlink( $file );
2546	}
2547	return;
2548	}
2549
2550	if ( ! function_exists( 'get_sites' ) ) {
2551	return;
2552	}
2553
2554	$paths = array();
2555	foreach ( get_sites( array( 'number' => 0 ) ) as $site ) {
2556	$prefix = self::path_prefix_segment( (string) $site->path );
2557	if ( '' !== $prefix ) {
2558	// Store the raw path so the drop-in can prefix-match a URI,
2559	// alongside the segment it maps to.
2560	$paths[ trim( (string) $site->path, '/' ) ] = $prefix;
2561	}
2562	}
2563
2564	if ( empty( $paths ) ) {
2565	if ( file_exists( $file ) ) {
2566	// phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink, WordPress.PHP.NoSilencedErrors.Discouraged -- see above.
2567	@unlink( $file );
2568	}
2569	return;
2570	}
2571
2572	// Longest path first so /a/b wins over /a.
2573	uksort(
2574	$paths,
2575	static function ( $x, $y ) {
2576	return strlen( (string) $y ) <=> strlen( (string) $x );
2577	}
2578	);
2579
2580	$lines = array();
2581	foreach ( $paths as $raw => $segment ) {
2582	$lines[] = $raw . '\|' . $segment;
2583	}
2584
2585	if ( ! is_dir( XSPEED_CACHE_DIR ) && ! wp_mkdir_p( XSPEED_CACHE_DIR ) ) {
2586	return;
2587	}
2588	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents -- read by the pre-WP drop-in; WP_Filesystem needs admin credentials unavailable here.
2589	file_put_contents( $file, implode( "\n", $lines ), LOCK_EX );
2590	}
2591
2592	public static function sync_mobile_flag( $enabled = null ): void {
2593	if ( null === $enabled ) {
2594	$opts = Settings_Manager::get( 'cache' );
2595	$enabled = ! empty( $opts['mobile_separate'] );
2596	}
2597	$dir = XSPEED_CACHE_DIR;
2598	$flag = $dir . '/.mobile-separate';
2599	if ( $enabled ) {
2600	if ( ! is_dir( $dir ) && ! wp_mkdir_p( $dir ) ) {
2601	return;
2602	}
2603	if ( ! file_exists( $flag ) ) {
2604	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_touch, WordPress.PHP.NoSilencedErrors.Discouraged -- read by the pre-WP drop-in via file_exists(); must be a plain marker, not WP_Filesystem.
2605	@touch( $flag );
2606	}
2607	return;
2608	}
2609	if ( file_exists( $flag ) ) {
2610	// phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink, WordPress.PHP.NoSilencedErrors.Discouraged -- plain marker removal; non-fatal.
2611	@unlink( $flag );
2612	}
2613	}
2614
2615	/**
2616	* Write / remove the `.maintenance-active` sentinel next to the cache
2617	* files. The pre-WP drop-in checks for this marker and bails when present,
2618	* so a page cached while the site was live is NOT served during
2619	* maintenance / coming-soon mode — WordPress loads and renders the
2620	* maintenance screen instead. The Pro Maintenance-Cache module drives this
2621	* on the maintenance on/off transition. (FBS-82409 B1)
2622	*
2623	* @param bool $active True to arm the sentinel (entering maintenance),
2624	* false to clear it (site recovered).
2625	*/
2626	public static function sync_maintenance_flag( bool $active ): void {
2627	$dir = XSPEED_CACHE_DIR;
2628	$flag = $dir . '/.maintenance-active';
2629	if ( $active ) {
2630	if ( ! is_dir( $dir ) && ! wp_mkdir_p( $dir ) ) {
2631	return;
2632	}
2633	if ( ! file_exists( $flag ) ) {
2634	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_touch, WordPress.PHP.NoSilencedErrors.Discouraged -- read by the pre-WP drop-in via file_exists(); must be a plain marker, not WP_Filesystem.
2635	@touch( $flag );
2636	}
2637	return;
2638	}
2639	if ( file_exists( $flag ) ) {
2640	// phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink, WordPress.PHP.NoSilencedErrors.Discouraged -- plain marker removal; non-fatal.
2641	@unlink( $flag );
2642	}
2643	}
2644
2645	/**
2646	* Reconcile every mobile_separate-dependent artifact to the current
2647	* setting. Called on boot and whenever the cache settings are saved, so
2648	* flipping mobile_separate at runtime can't leave the install in a
2649	* half-converted state.
2650	*
2651	* Three things must agree with the setting:
2652	* 1. the drop-in's `.mobile-separate` flag (sync_mobile_flag()),
2653	* 2. the device-blind server rewrite — present only when OFF
2654	* (static_rewrite_allowed()),
2655	* 3. the now-stale static-cache tree + page cache, which were keyed
2656	* under the old scheme and would serve wrong-device HTML.
2657	*
2658	* No-ops when the cache is disabled — there's nothing installed to
2659	* reconcile, and toggle() handles install/teardown itself.
2660	*/
2661	public static function reconcile_mobile_separate(): void {
2662	self::sync_mobile_flag();
2663	// Keep the drop-in's view of the network's blog paths current — a
2664	// site added or removed changes which bucket its URLs belong to. (#6)
2665	if ( defined( 'XSPEED_CACHE_DIR' ) ) {
2666	self::sync_site_paths();
2667	}
2668
2669	// The rewrite/static reconciliation below needs the plugin's path
2670	// constants. They're absent in early-boot / unit-test contexts where
2671	// only the drop-in flag matters — bail to the flag-only behavior then.
2672	if ( ! defined( 'XSPEED_CACHE_STATIC_DIR' ) ) {
2673	return;
2674	}
2675
2676	// Only touch the rewrite + caches when caching is actually on.
2677	$opts = get_option( 'xspeed_options', array() );
2678	if ( empty( $opts['cache_enabled'] ) ) {
2679	return;
2680	}
2681
2682	$rewrite_present = self::rewrite_installed();
2683	$rewrite_wanted = self::static_rewrite_allowed();
2684
2685	// Did the thing that actually invalidates cache KEYS change?
2686	// mobile_separate buckets entries as \|d / \|m, so flipping it makes
2687	// stored entries mis-bucketed and they must go. A rewrite-state
2688	// mismatch from anything else (e.g. mod_headers detection, a hand-
2689	// edited .htaccess) changes no key at all — the same files are still
2690	// valid, they're just served by PHP instead of by the web server.
2691	// Purging there is what let one WP-CLI call wipe the whole cache on
2692	// every bootstrap. (#138)
2693	//
2694	// Read the setting from the SAME place static_rewrite_allowed() and
2695	// sync_mobile_flag() do — the cache module's settings, not the
2696	// top-level xspeed_options — or this marker would track a key that
2697	// never changes and a real flip would go unnoticed.
2698	$cache_opts = Settings_Manager::get( 'cache' );
2699	$mobile_now = ! empty( $cache_opts['mobile_separate'] );
2700	$mobile_last = get_option( 'xspeed_last_mobile_separate', null );
2701	$mobile_flipped = ( null !== $mobile_last && (bool) (int) $mobile_last !== $mobile_now );
2702
2703	if ( (string) (int) $mobile_now !== (string) $mobile_last ) {
2704	update_option( 'xspeed_last_mobile_separate', $mobile_now ? '1' : '0', false );
2705	}
2706
2707	if ( $rewrite_present === $rewrite_wanted ) {
2708	// Already consistent — nothing flipped, leave caches intact so a
2709	// plain settings save (e.g. expiry change) doesn't blow the cache.
2710	return;
2711	}
2712
2713	// Bring the rewrite into line with what this server actually supports.
2714	if ( $rewrite_wanted ) {
2715	self::install_rewrite();
2716	} else {
2717	self::remove_rewrite();
2718	}
2719
2720	// Only discard cache contents when the device bucketing changed.
2721	if ( $mobile_flipped ) {
2722	self::purge_all( 'mobile_separate changed' );
2723	}
2724	}
2725
2726	/**
2727	* Whether the server-level static-rewrite fast path may be used.
2728	*
2729	* The rewrite serves `{host}{path}/index.html` straight from the web
2730	* server, keyed only by host + path — it has no way to run our PHP
2731	* device detection, so it can't tell mobile from desktop. When
2732	* `mobile_separate` is on, a single static file would be shared across
2733	* devices and whoever primed it wins (mobile visitors could get desktop
2734	* HTML, or vice-versa). Rather than duplicate a wp_is_mobile()-equivalent
2735	* UA matcher into .htaccess AND the nginx snippet (three copies that
2736	* would inevitably drift), we simply DON'T engage the static rewrite when
2737	* mobile_separate is on. Requests then fall through to the PHP drop-in,
2738	* which buckets correctly — a small TTFB cost (~85ms vs ~30ms) paid only
2739	* on mobile-separate sites, in exchange for guaranteed correctness.
2740	*
2741	* LiteSpeed exclusion (2026-06-16): on LiteSpeed — OpenLiteSpeed in
2742	* particular — `.htaccess` CAN run our RewriteRule to serve the static
2743	* file, but its `.htaccess` engine ignores `mod_headers`, so we cannot
2744	* stamp the served response with `X-XSpeed-Cache: HIT`, AND there is no
2745	* `.htaccess` equivalent of nginx's per-location `access_log` to record
2746	* the hit. The result was a cache that worked but was invisible: no HIT
2747	* header and a hit-ratio frozen near 0%. Every OTHER server gives the
2748	* user a visible HIT header + a counted hit (nginx via add_header +
2749	* access_log in its snippet; Apache via the `<IfModule mod_headers.c>`
2750	* block in rewrite_block_lines(), WHEN that module is loaded — when it is
2751	* not, Apache takes this same drop-in fallback). To keep LiteSpeed
2752	* CONSISTENT with the rest, we route its hits
2753	* through the PHP drop-in instead — the drop-in emits
2754	* `X-XSpeed-Cache: HIT (php)` and calls Hit_Counter inline, exactly the
2755	* observable behavior the other servers get. The cost is the drop-in's
2756	* ~30ms TTFB vs the static path's ~10ms, paid only on LiteSpeed; in
2757	* exchange the dashboard hit-ratio and the response header finally tell
2758	* the truth there. (Apache keeps the static fast path — it honors the
2759	* header.) See maybe_emit_lscache_headers() for the paired LSCache
2760	* stand-down that stops LiteSpeed's own module from shadowing the
2761	* drop-in.
2762	*/
2763	public static function static_rewrite_allowed(): bool {
2764	// LiteSpeed: drop-in serves hits (visible + counted) — see docblock.
2765	if ( Server::LITESPEED === Server::type() ) {
2766	return false;
2767	}
2768	// Apache without mod_headers is in EXACTLY the position LiteSpeed
2769	// is in above: it can run the RewriteRule and serve the static
2770	// file, but it cannot stamp `X-XSpeed-Cache` on the response, so
2771	// the hit is invisible to the user and uncountable by
2772	// Hit_Counter. The docblock above used to assert Apache "honors
2773	// mod_headers" and left it on the fast path unconditionally —
2774	// true only when the module is actually loaded. Fall back to the
2775	// drop-in when it isn't, trading ~10ms of TTFB for a hit that
2776	// shows up in the header and the ratio. (Field report: hit ratio
2777	// pinned at 0% on a working Apache cache.)
2778	if ( Server::APACHE === Server::type() && ! Server::apache_has_mod_headers() ) {
2779	return false;
2780	}
2781	$opts = Settings_Manager::get( 'cache' );
2782	return empty( $opts['mobile_separate'] );
2783	}
2784
2785	/**
2786	* Why the device-blind static rewrite is NOT installed, when it isn't.
2787	* Returns 'mobile_separate' when Separate Mobile Cache is the blocker
2788	* (the static file is one-per-URL, so it can't coexist with per-device
2789	* buckets), 'no_mod_headers' when Apache can't stamp the HIT header,
2790	* '' otherwise. Lets the dashboard explain the slow path instead of
2791	* silently falling back to PHP serving. (FBS-83145)
2792	*
2793	* Every refusal in static_rewrite_allowed() that is NOT self-explanatory
2794	* must have a branch here. Otherwise the Health card falls through to
2795	* "Block missing — toggle Enable Cache off and on to reinstall it",
2796	* advice that cannot work: the same condition that suppressed the write
2797	* suppresses the reinstall, and auto_heal() strips the block again on
2798	* the next admin page load. (Field report: Apache host with mod_headers
2799	* unloaded sat on the slow path with no way to find out why.)
2800	*/
2801	/**
2802	* Qualify a raw probe result with what we already KNOW about config.
2803	*
2804	* probe_static_rewrite() writes its own file under the static-cache tree
2805	* and fetches that, which succeeds whenever the web server can serve a
2806	* static file at all — including when static_rewrite_allowed() is false
2807	* and no real page is on the static path. So `active: true` on its own is
2808	* not evidence that pages are being served statically.
2809	*
2810	* The reachable case is nginx with Separate Mobile Cache on: the snippet
2811	* lives in the server block and we cannot remove it, pages are
2812	* deliberately routed to the PHP drop-in, but the probe file is still
2813	* served directly.
2814	*
2815	* The Health panel learned this in 88b4b50; the CLI, REST and MCP paths
2816	* did not, so they kept reporting "active" in exactly that configuration.
2817	* Rather than repeat the reasoning at each call site, they now all come
2818	* through here.
2819	*
2820	* Deliberately does NOT consult rewrite_installed(): on nginx the fast
2821	* path is the pasted snippet and there is no .htaccess marker to find, so
2822	* requiring one would report every correctly-configured nginx site as
2823	* broken.
2824	*
2825	* @param array $probe Raw result from probe_static_rewrite().
2826	* @return array{active:bool,inconclusive:bool,reason:string,block_reason:string}
2827	*/
2828	public static function qualify_rewrite_probe( array $probe ): array {
2829	$active = (bool) ( $probe['active'] ?? false );
2830	$inconclusive = (bool) ( $probe['inconclusive'] ?? false );
2831	$reason = (string) ( $probe['reason'] ?? '' );
2832	$block_reason = self::static_rewrite_block_reason();
2833
2834	// With page caching off there is nothing to serve, so `active` can
2835	// never be true here whatever the raw probe says. probe_static_rewrite()
2836	// writes its OWN file under the static tree and fetches that, which
2837	// succeeds whenever the server can serve a static file at all — and on
2838	// nginx the snippet is server-level, so it keeps succeeding after the
2839	// cache is switched off.
2840	//
2841	// block_reason() used to carry this meaning by accident: it returned
2842	// 'mobile_separate' with caching off, and the refusal branch below
2843	// forced active=false. Now that it correctly reports '' (nothing can
2844	// block a fast path that isn't in use), this consumer has to state the
2845	// condition itself — otherwise `wp xspeed cache recheck-rewrite` and
2846	// POST /cache/recheck-rewrite claim "the web server is serving cache
2847	// hits directly" on a site with no cache. That is a positive false
2848	// claim rather than a nag, i.e. worse than the bug being fixed.
2849	$cache_opts = Settings::get();
2850	if ( empty( $cache_opts['cache_enabled'] ) ) {
2851	return array(
2852	'active' => false,
2853	'inconclusive' => false,
2854	'reason' => 'Page caching is off, so there is no cache for the web server to serve.',
2855	'block_reason' => '',
2856	);
2857	}
2858
2859	// A known refusal outranks the probe, and also outranks
2860	// "inconclusive" — a blocked rewrite whose probe merely failed to
2861	// complete is still definitely blocked.
2862	if ( '' !== $block_reason ) {
2863	$active = false;
2864	$inconclusive = false;
2865	$reason = self::block_reason_text( $block_reason );
2866	}
2867
2868	return array(
2869	'active' => $active,
2870	'inconclusive' => $inconclusive,
2871	'reason' => $reason,
2872	'block_reason' => $block_reason,
2873	);
2874	}
2875
2876	/**
2877	* Human-readable explanation for a static_rewrite_block_reason() code.
2878	*
2879	* Each one has to say what to DO about it: "mobile_separate" alone tells
2880	* a user nothing, and the whole point of surfacing a refusal instead of
2881	* the probe verdict is that it is actionable.
2882	*/
2883	public static function block_reason_text( string $code ): string {
2884	switch ( $code ) {
2885	case 'mobile_separate':
2886	return 'Separate Mobile Cache is on, which disables the device-blind static rewrite. Cache hits are served by PHP instead. If your site serves the same HTML to every device, turn it off in Cache settings for much faster hits.';
2887	case 'no_mod_headers':
2888	return "Apache's mod_headers is not loaded, so the static rewrite cannot mark its responses as cache hits. Enable mod_headers, or leave hits on the PHP path.";
2889	default:
2890	return sprintf( 'The static rewrite is disabled (%s).', $code );
2891	}
2892	}
2893
2894	public static function static_rewrite_block_reason(): string {
2895	// Nothing can be blocking the fast path when there is no cache to
2896	// serve from it. Without this the dashboard told users with page
2897	// caching switched OFF that Separate Mobile Cache "is disabling
2898	// faster static serving" — a fast path they were not using, about a
2899	// cache that did not exist. Every caller of this is a user-facing
2900	// explanation of why the rewrite is off, so "the cache is off" is
2901	// the honest answer, and it is silence. (#108)
2902	$opts = Settings::get();
2903	if ( empty( $opts['cache_enabled'] ) ) {
2904	return '';
2905	}
2906	if ( Server::LITESPEED === Server::type() ) {
2907	return ''; // Intended on LiteSpeed — not a "block".
2908	}
2909	if ( Server::APACHE === Server::type() && ! Server::apache_has_mod_headers() ) {
2910	return 'no_mod_headers';
2911	}
2912	$cache_opts = Settings_Manager::get( 'cache' );
2913	return ! empty( $cache_opts['mobile_separate'] ) ? 'mobile_separate' : '';
2914	}
2915
2916	/**
2917	* Whether migration flagged Separate Mobile Cache for user review. Set by
2918	* Migration::map_mobile_separate() when a source plugin (WP Rocket / WP
2919	* Super Cache / LiteSpeed) had its "separate mobile cache" option on: we
2920	* import it as OFF (to keep the device-blind static fast path) but record
2921	* this flag so the dashboard can invite the user to turn it back on only
2922	* if their site genuinely serves different HTML per device. (FBS-83145)
2923	*/
2924	public static function mobile_separate_needs_review(): bool {
2925	// Same reasoning as static_rewrite_block_reason(): the invitation is
2926	// "turn this back on if your site needs it, to regain the fast path",
2927	// which is meaningless with page caching off — there is no fast path
2928	// to regain, and the equality probe behind the prompt would fetch
2929	// pages that aren't being cached. Gated here rather than at the two
2930	// payload call sites (Admin + Rest_Api) so `enabled`, `blocking` and
2931	// `needs_review` are consistently gated on the same condition. (#108)
2932	$opts = Settings::get();
2933	if ( empty( $opts['cache_enabled'] ) ) {
2934	return false;
2935	}
2936	$cache_opts = Settings_Manager::get( 'cache' );
2937	return ! empty( $cache_opts['mobile_separate_review'] );
2938	}
2939
2940	/**
2941	* Clear the review flag — called when the user has acted on the prompt
2942	* (dismissed it, or turned Separate Mobile Cache on/off deliberately) so
2943	* the dashboard callout doesn't nag forever. Writes the option directly
2944	* (bypassing Settings_Manager) so it never touches schema fields.
2945	*/
2946	public static function clear_mobile_separate_review(): void {
2947	$stored = get_option( 'xspeed_module_cache', array() );
2948	if ( ! is_array( $stored ) \|\| empty( $stored['mobile_separate_review'] ) ) {
2949	return;
2950	}
2951	unset( $stored['mobile_separate_review'] );
2952	update_option( 'xspeed_module_cache', $stored );
2953	}
2954
2955	/**
2956	* On-demand probe: does the homepage serve materially the same HTML to a
2957	* desktop and a mobile browser? Fetches home_url() twice over loopback —
2958	* once with a desktop User-Agent, once with a mobile one — strips
2959	* per-request noise (nonces, CSRF tokens, session ids, inline timestamps),
2960	* and compares. When identical, Separate Mobile Cache is almost certainly
2961	* unnecessary and the user can turn it off to regain the static fast path.
2962	*
2963	* NEVER run automatically (no page-load cost) — only from the dashboard
2964	* "Check now" button. Result is cached for 10 minutes so a double-click or
2965	* a re-render doesn't fire two more self-requests. (FBS-83145)
2966	*
2967	* @return array{ identical:bool, checked:bool, reason?:string, desktop_bytes?:int, mobile_bytes?:int }
2968	*/
2969	public static function probe_mobile_equality(): array {
2970	$cached = get_transient( 'xspeed_mobile_equality_probe' );
2971	if ( is_array( $cached ) ) {
2972	return $cached;
2973	}
2974
2975	$home = home_url( '/' );
2976	$host = (string) wp_parse_url( $home, PHP_URL_HOST );
2977	if ( '' === $host ) {
2978	$result = array( 'identical' => false, 'checked' => false, 'reason' => 'home_url has no host' );
2979	set_transient( 'xspeed_mobile_equality_probe', $result, MINUTE_IN_SECONDS );
2980	return $result;
2981	}
2982
2983	// Match WP core's own mobile detection (wp_is_mobile) so the probe
2984	// reflects what the site would actually branch on. iPhone Safari for
2985	// mobile; a current desktop Chrome UA for desktop.
2986	$desktop_ua = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36';
2987	$mobile_ua = 'Mozilla/5.0 (iPhone; CPU iPhone OS 17_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.0 Mobile/15E148 Safari/604.1';
2988
2989	$is_local = function_exists( 'wp_get_environment_type' )
2990	&& in_array( wp_get_environment_type(), array( 'local', 'development' ), true );
2991
2992	$fetch = static function ( string $ua ) use ( $home, $is_local ) {
2993	$resp = wp_remote_get(
2994	$home,
2995	array(
2996	'timeout' => 5,
2997	'sslverify' => ! $is_local,
2998	'redirection' => 2,
2999	// Bust any per-device cache so we compare freshly-rendered
3000	// HTML, and pass the device UA the site would branch on.
3001	'user-agent' => $ua,
3002	'headers' => array( 'Cache-Control' => 'no-cache' ),
3003	)
3004	);
3005	if ( is_wp_error( $resp ) \|\| 200 !== (int) wp_remote_retrieve_response_code( $resp ) ) {
3006	return null;
3007	}
3008	return (string) wp_remote_retrieve_body( $resp );
3009	};
3010
3011	$desktop = $fetch( $desktop_ua );
3012	$mobile = $fetch( $mobile_ua );
3013
3014	if ( null === $desktop \|\| null === $mobile ) {
3015	$result = array( 'identical' => false, 'checked' => false, 'reason' => 'could not fetch homepage twice' );
3016	set_transient( 'xspeed_mobile_equality_probe', $result, MINUTE_IN_SECONDS );
3017	return $result;
3018	}
3019
3020	$identical = self::normalize_html_for_diff( $desktop ) === self::normalize_html_for_diff( $mobile );
3021
3022	$result = array(
3023	'identical' => $identical,
3024	'checked' => true,
3025	'desktop_bytes' => strlen( $desktop ),
3026	'mobile_bytes' => strlen( $mobile ),
3027	);
3028	set_transient( 'xspeed_mobile_equality_probe', $result, 10 * MINUTE_IN_SECONDS );
3029	return $result;
3030	}
3031
3032	/**
3033	* Strip per-request noise from HTML so a desktop-vs-mobile diff reflects
3034	* real structural differences, not nonces / session ids / timestamps that
3035	* change on every render. Deliberately conservative: it normalizes the
3036	* handful of well-known noise sources and collapses whitespace, so a site
3037	* that truly serves different markup per device still compares as different.
3038	*/
3039	private static function normalize_html_for_diff( string $html ): string {
3040	// Every rule here errs toward "they differ" being WRONG rather than
3041	// "they match" being wrong: this check only ever tells a user it is
3042	// SAFE to turn Separate Mobile Cache off, so a false "identical"
3043	// would cost them device-specific output. The risk of being too
3044	// conservative is milder but real — the useful answer never appears,
3045	// and the feature's whole pitch ("we'll prove it's safe to turn
3046	// off") silently never pays out. These close the gaps that made a
3047	// mismatch effectively guaranteed on an ordinary WordPress site. (#108)
3048	$patterns = array(
3049	// WP nonces in attribute or JSON form: data-nonce="…",
3050	// _wpnonce=…, "nonce":"…". The `[:=]` adjacency below misses
3051	// wp_nonce_field()'s own markup — `name="_wpnonce" value="ab…"`
3052	// puts `value=` between the key and the token — which is the
3053	// single most common nonce shape in WordPress, so that form is
3054	// matched explicitly first.
3055	'/name=["\']?(_wpnonce\|_ajax_nonce)["\']?\s+value=["\']?[a-z0-9]{8,}/i',
3056	// CSP nonces on script/style tags. Base64, so uppercase and
3057	// +/= appear — the hex-only rules below can never match one,
3058	// and a CSP-enabled site therefore differed on every fetch.
3059	// MUST precede the generic nonce rule: that one stops at the
3060	// first non-alphanumeric, leaving the rest of the token behind
3061	// and the two responses still unequal.
3062	// The quotes are optional so HTML5's legal unquoted attribute
3063	// form (`<script nonce=AbCd+q/r=>`) is covered too — without
3064	// that it fell through to the generic rule, which is the exact
3065	// failure this rule exists to remove.
3066	'/\bnonce=(["\'])?[A-Za-z0-9+\/=_-]{8,}(?(1)\1)/',
3067	'/(_wpnonce\|nonce\|_ajax_nonce)["\']?\s[:=]\s["\']?[a-z0-9]{8,}/i',
3068	// Generic hex tokens: cache busters, session ids, md5/sha
3069	// digests. Was 16+, which left an 11-15 char gap above the
3070	// 10-char nonce rule.
3071	//
3072	// The token MUST contain at least one a-f letter. `[a-f0-9]`
3073	// also matches every decimal digit, so a bare `{10,}` erased
3074	// every 10+ digit INTEGER anywhere in the document — including
3075	// visible body text. A page whose desktop and mobile HTML
3076	// differed only by a per-device numeric id (an AdSense slot, an
3077	// A/B bucket, an analytics property) then compared as identical,
3078	// and the check told the user it was safe to switch off the very
3079	// setting keeping that output correct — the one direction this
3080	// function must never fail in. Decimal-only runs are left to the
3081	// bounded epoch rule below, which is deliberately narrower.
3082	//
3083	// Known, accepted (QA R2): a token whose letters all fall in a-f
3084	// reads as a digest, so a per-device `ABC1234567890` strips even
3085	// though it is an id, not a hash. Deliberately left open — the
3086	// alternatives all cost more than the bug:
3087	//
3088	// Token shape (lowercase-only, case-uniformity, a trailing
3089	// letter) cannot separate it. `ABC1234567890` and
3090	// `ABCDEF012345` — an uppercase digest this rule SHOULD strip —
3091	// are both all-hex, uniformly cased, letters-then-digits.
3092	// Each variant fixed the id only by sparing the digest.
3093	//
3094	// Letter density does separate them (23% letters vs 50%), but
3095	// measured over 2000 md5/sha1/sha256 samples, requiring letters
3096	// spread through the token leaves 21-67% of REAL digests
3097	// unmatched depending on the window. Digest noise is most of
3098	// what this function exists to remove, so that trade guts it.
3099	//
3100	// Context (protecting data-* attribute values from this rule)
3101	// works for ids and still strips digests in URLs, classes and
3102	// query strings — but regresses a CHANGING digest inside a
3103	// non-nonce data-* attribute, and needs a two-pass
3104	// hold/restore. Viable if R2 is ever worth pressing; its
3105	// failure at least errs toward "differ".
3106	//
3107	// An A-F-only prefix on a per-device id is rare, and the earlier
3108	// nonce rules already claim the data-nonce/_wpnonce shapes.
3109	'/\b(?=[a-f0-9]{10,}\b)[0-9][a-f][a-f0-9]\b/i',
3110	// wp-generated unique ids (e.g. wp-block ids, aria ids).
3111	'/(id\|for\|aria-[a-z]+)="[^"]*-[0-9]{3,}"/i',
3112	// ISO-ish timestamps + epoch-looking numbers in query strings.
3113	'/\?ver=[0-9.]+/',
3114	'/[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9:.+Z-]+/',
3115	// Raw epoch seconds. The two fetches are sequential, so any
3116	// template printing time() guaranteed a mismatch.
3117	//
3118	// This is the ONLY rule that may strip a decimal-only run, so
3119	// its bound is load-bearing rather than decorative — every digit
3120	// it gives away is a class of per-device id it silently erases.
3121	// `1[0-9]{9}` was too loose: it claimed the whole
3122	// 1000000000-1999999999 range (2001-2033) to cover timestamps
3123	// nobody serves, and took every 10-digit AdSense slot, order id
3124	// and SKU beginning with 1 along with it — reproducing the exact
3125	// false-"identical" verdict the hex rule above was tightened to
3126	// stop. `1[6-9]` covers 2020-2033, which is the only span a live
3127	// site can actually print, and collides with roughly a tenth as
3128	// many ids.
3129	//
3130	// Not airtight — an id beginning 16-19 still collides. Closing
3131	// that properly means scoping this to places a timestamp really
3132	// appears (an attribute value, a query parameter, a JSON value)
3133	// rather than bare body text; the bound is the cheap 90% of it.
3134	'/\b1[6-9][0-9]{8}\b/',
3135	);
3136	$html = (string) preg_replace( $patterns, 'X', $html );
3137	// Collapse all whitespace so trivial formatting differences don't count.
3138	return trim( (string) preg_replace( '/\s+/', ' ', $html ) );
3139	}
3140
3141	public static function ensure_hits_log_file(): bool {
3142	// TWO writers append to this log, and an earlier fix conflated them:
3143	//
3144	// 1. nginx, via the server-level `access_log` directive in
3145	// nginx_snippet() — a DIFFERENT uid, which is why the file needs
3146	// to be world-writable there.
3147	// 2. the PHP drop-in (advanced-cache.php), on EVERY server. A hit it
3148	// serves bypasses WordPress entirely, so it can't call
3149	// Hit_Counter::record_hit() — appending here is the only way that
3150	// hit is ever counted.
3151	//
3152	// The nginx-only early return that used to sit at the top of this
3153	// method was fixing something real: chmod() on a file PHP doesn't own
3154	// raises "Operation not permitted", and off nginx that chmod buys
3155	// nothing. But it took directory creation with it, so on LiteSpeed
3156	// (which always serves via the drop-in), on Apache without mod_headers,
3157	// and anywhere mobile_separate forces the drop-in path, writer 2 was
3158	// appending to a file whose parent directory did not exist. The append
3159	// is @-suppressed and documented as non-fatal, so every one of those
3160	// hits vanished and the dashboard ratio sat at 0% forever.
3161	//
3162	// So: create the dir + file everywhere, and keep only the chmod gated
3163	// to nginx.
3164	$dir = self::hits_log_dir();
3165	if ( ! is_dir( $dir ) && ! wp_mkdir_p( $dir ) ) {
3166	return false;
3167	}
3168
3169	$is_nginx = ( Server::NGINX === Server::type() );
3170
3171	if ( $is_nginx ) {
3172	// Ensure the dir is traversable + writable by a different-uid nginx.
3173	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_chmod -- nginx (a separate uid in multi-container setups) must be able to create/append the log; WP_Filesystem layers ownership overrides that defeat that intent.
3174	@chmod( $dir, 0777 ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- best-effort; the access_log just stays empty if it fails.
3175	}
3176
3177	$path = self::hits_log_path();
3178	if ( ! file_exists( $path ) ) {
3179	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_touch -- See docblock: must be a plain touch, not WP_Filesystem.
3180	@touch( $path ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- non-fatal helper; failures already covered by the dir check.
3181	}
3182
3183	if ( $is_nginx ) {
3184	// World-writable so a different-uid nginx can append HIT lines.
3185	// Off nginx the drop-in appends as the same uid that owns the file,
3186	// so this is unnecessary — and would emit the "Operation not
3187	// permitted" warnings the old early return was added to silence.
3188	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_chmod -- See docblock.
3189	@chmod( $path, 0666 ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- best-effort.
3190	}
3191
3192	return file_exists( $path );
3193	}
3194
3195	public static function nginx_snippet(): ?string {
3196	if ( Server::NGINX !== Server::type() ) {
3197	return null;
3198	}
3199	$rel = '/' . ltrim( str_replace( ABSPATH, '/', XSPEED_CACHE_STATIC_DIR ), '/' );
3200	$rel = rtrim( $rel, '/' );
3201
3202	// WP-Rocket-canonical pattern: every condition lives at
3203	// SERVER level (outside any location block). Each one appends
3204	// a tag to $xspeed_no_cache; the final check is a single
3205	// string-equality against the unmodified default "no-cache".
3206	// Only when ALL conditions pass does the rewrite fire,
3207	// jumping the request to the static file's URL. nginx then
3208	// restarts location matching against the new path, where
3209	// regular static-file serving takes over.
3210	//
3211	// Why server-level + a single rewrite (instead of try_files
3212	// inside `location /`): nginx's well-documented "if is evil"
3213	// quirk silently disables `try_files`'s last fallback when
3214	// any `if` in the same location is true. Moving the `if`s
3215	// outside any location dodges the trap completely, because
3216	// server-level rewrite is the documented stable path.
3217	//
3218	// `last` (not `break`) restarts location matching — required
3219	// so the rewritten static-file URI gets served via the normal
3220	// static-file location, not re-matched against `location /`
3221	// where our own rewrite would loop.
3222	//
3223	// The cache existence check is the LAST condition in the
3224	// chain so when the file isn't cached, $xspeed_no_cache
3225	// gets a "-nofile" tag and the rewrite is skipped — the
3226	// request falls through to whatever `location /` the user
3227	// already had (typically `try_files $uri $uri/ /index.php?$args;`).
3228	// Absolute path to the hit-log file from the nginx process's
3229	// filesystem view. Nginx's `access_log buffer=N flush=Ns` form
3230	// requires a literal path — `$document_root` variables are
3231	// rejected — so PHP computes it. Lives under uploads/ (NOT the
3232	// cache dir): a cache purge or uninstall deletes the cache dir,
3233	// which would orphan this directive's parent directory and make
3234	// `nginx -t` fail [emerg] for EVERY vhost on the host
3235	// (FBS-82478). uploads/ survives both, so the directive can
3236	// never take nginx down. Works on every topology where the nginx
3237	// process shares a filesystem with PHP (container or host).
3238	$hits_abs = self::hits_log_path();
3239
3240	$lines = array();
3241	$lines[] = '# xSpeed static cache — paste at server level, above location / { }.';
3242	// Cache host must match the on-disk dir PHP writes: store_static() /
3243	// static_host() take HTTP_HOST and strip every char outside
3244	// [a-zA-Z0-9.\-] — i.e. it removes the colon but KEEPS the port digits
3245	// (localhost:8192 → localhost8192). nginx's own $host can't reproduce
3246	// that: $host has the port already stripped ENTIRELY (→ localhost), so
3247	// the -f check looks for localhost/... while PHP wrote localhost8192/...
3248	// and the rewrite never fires on a non-standard port. Derive
3249	// $xspeed_host from $http_host (which keeps the port) and drop just the
3250	// colon, so it equals the PHP dir on every port. On standard ports
3251	// $http_host has no colon, so $xspeed_host == $host == the bare domain.
3252	$lines[] = 'set $xspeed_host $http_host;'; // default: no port → unchanged (e.g. example.com)
3253	$lines[] = 'if ($http_host ~ "^([^:]+):(\\d+)$") { set $xspeed_host $1$2; }'; // host:port → hostport (matches PHP static_host())
3254	$lines[] = 'set $xspeed_no_cache "no-cache";';
3255	$lines[] = 'if ($request_method != GET) { set $xspeed_no_cache "$xspeed_no_cache-method"; }';
3256	$lines[] = 'if ($args) { set $xspeed_no_cache "$xspeed_no_cache-args"; }';
3257	// Cookie + user-agent exclusions, generated from the user's actual
3258	// settings rather than a hardcoded list. Before this, the rule
3259	// tested three fixed cookie names and no user agent at all, so
3260	// every excluded_cookies / bypass_user_agents entry applied only
3261	// while a page was cold — on a warm page nginx served the shared
3262	// anonymous copy to carts, members and bypassed bots alike. The
3263	// three historical names survive as a floor inside cookie_rule().
3264	// `~*` is case-insensitive, matching PHP's stripos()/glob checks.
3265	$cache_opts = Settings_Manager::get( 'cache' );
3266	$cookie_rule = Server_Rules::cookie_rule(
3267	is_array( $cache_opts['excluded_cookies'] ?? null ) ? $cache_opts['excluded_cookies'] : array()
3268	);
3269	$lines[] = 'if ($http_cookie ~* "(' . $cookie_rule['regex'] . ')") { set $xspeed_no_cache "$xspeed_no_cache-cookie"; }';
3270
3271	$ua_rule = Server_Rules::user_agent_rule(
3272	is_array( $cache_opts['bypass_user_agents'] ?? null ) ? $cache_opts['bypass_user_agents'] : array()
3273	);
3274	// Emitted only when the list is non-empty — an empty alternation
3275	// would compile to `(...)` matching every request and disable the
3276	// fast path entirely.
3277	if ( '' !== $ua_rule['regex'] ) {
3278	$lines[] = 'if ($http_user_agent ~* "(' . $ua_rule['regex'] . ')") { set $xspeed_no_cache "$xspeed_no_cache-ua"; }';
3279	}
3280	$lines[] = 'if (!-f "$document_root' . $rel . '/$xspeed_host$uri/index.html") { set $xspeed_no_cache "$xspeed_no_cache-nofile"; }';
3281	// Neither `add_header` nor `access_log` is allowed inside an `if{}`
3282	// at server level (nginx rejects with "directive is not allowed
3283	// here"). The logging therefore lives in a `location` block that
3284	// matches the rewritten URI after `rewrite … last;` restarts
3285	// location matching. Every HIT lands there exactly once, every
3286	// MISS / PHP-served request never matches it.
3287	$lines[] = 'if ($xspeed_no_cache = "no-cache") {';
3288	$lines[] = ' rewrite ^ ' . $rel . '/$xspeed_host$uri/index.html last;';
3289	$lines[] = '}';
3290	$lines[] = '';
3291	$lines[] = '# Serve + log the cached HIT — `^~` is required so this beats any regex location.';
3292	$lines[] = 'location ^~ ' . $rel . '/ {';
3293	$lines[] = ' internal;';
3294	// LITERAL log path (not `set $var; access_log $var`). The variable form
3295	// makes nginx open the log lazily per-request and SILENTLY drop the
3296	// line if the open fails — so on a working host hits were served
3297	// (X-XSpeed-Cache fires regardless) but nothing was ever written and
3298	// the hit ratio sat at 0%. A literal path makes nginx open the file at
3299	// config load and actually log every hit.
3300	//
3301	// Deleting the log FILE is still safe with a literal path: nginx
3302	// recreates it on the next write/reload and `nginx -t` stays green
3303	// (verified). The only thing that [emerg]s `nginx -t` is a missing
3304	// parent DIRECTORY — and the log lives under uploads/xspeed/, which
3305	// survives cache purge + uninstall, and which ensure_hits_log_file()
3306	// (run on every admin_init via auto_heal) recreates if it ever goes
3307	// missing. So: hits are logged, and a user deleting the log can't take
3308	// nginx down.
3309	$lines[] = ' access_log ' . $hits_abs . ' combined buffer=16k flush=5s;';
3310	$lines[] = ' add_header X-XSpeed-Cache "HIT (nginx)" always;';
3311	$lines[] = '}';
3312	return implode( "\n", $lines );
3313	}
3314
3315	/**
3316	* Aggregate every enabled module's nginx_directives() into one
3317	* pasteable server-block snippet. Replaces the per-module "paste
3318	* this snippet" notices with a single consolidated paste — every
3319	* future feature toggle just regenerates this output.
3320	*
3321	* Returns null on non-nginx hosts (nothing to paste).
3322	*
3323	* Sections render in module-registration order so the layout stays
3324	* predictable; each module gets a comment header `# <slug>`.
3325	*/
3326	public static function full_nginx_server_block(): ?string {
3327	if ( Server::NGINX !== Server::type() ) {
3328	return null;
3329	}
3330
3331	$blocks = array();
3332	foreach ( Module_Registry::all() as $module ) {
3333	$directives = $module->nginx_directives();
3334	if ( ! is_string( $directives ) \|\| '' === trim( $directives ) ) {
3335	continue;
3336	}
3337	$blocks[] = "# === " . $module->slug() . " ===\n" . rtrim( $directives );
3338	}
3339
3340	if ( empty( $blocks ) ) {
3341	return null;
3342	}
3343
3344	$header = "# xSpeed unified nginx config — paste into `server { }`, above `location / { }`; re-paste after toggling features.\n";
3345
3346	return $header . "\n" . implode( "\n\n", $blocks ) . "\n";
3347	}
3348
3349	/**
3350	* Tell LiteSpeed's LSCache module to stand down on the cache-miss
3351	* render path.
3352	*
3353	* History: this method used to emit X-LiteSpeed-Cache-Control:
3354	* public,max-age=N + X-LiteSpeed-Tag, handing caching to the server's
3355	* LSCache store. That delegation backfired — once LSCache cached a
3356	* page it served every subsequent request from its OWN store and
3357	* intercepted the request before our site-root .htaccess static
3358	* rewrite could run. Net effect on LiteSpeed hosts: no X-XSpeed-Cache
3359	* header, our static-cache tree never served, the HIT log never
3360	* written (hit ratio frozen at 0%), and the Health probe reporting a
3361	* false "cache running on PHP fallback" because it never saw an
3362	* xSpeed-served response.
3363	*
3364	* xSpeed now owns the cache on LiteSpeed exactly as it does on Apache:
3365	* our `.htaccess` mod_rewrite block serves hits straight from the
3366	* static-cache tree (with the X-XSpeed-Cache header + access-log HIT
3367	* accounting), and PHP/the drop-in is the fallback. To guarantee
3368	* LSCache doesn't shadow that with its own copy — some LiteSpeed
3369	* configs cache by default — we send an explicit `no-cache` control so
3370	* the server defers to our rewrite. Skipped when the LiteSpeed Cache
3371	* plugin is active (it owns its own header policy; our Conflict
3372	* registry handles that coexistence separately).
3373	*/
3374	public static function maybe_emit_lscache_headers(): void {
3375	if ( headers_sent() ) {
3376	return;
3377	}
3378	if ( Server::LITESPEED !== Server::type() ) {
3379	return;
3380	}
3381	// is_plugin_active() lives in wp-admin/includes/plugin.php which
3382	// isn't auto-loaded on front-end requests. Use the option layer
3383	// directly to avoid pulling in admin code from a render path.
3384	$active = (array) get_option( 'active_plugins', array() );
3385	if ( in_array( 'litespeed-cache/litespeed-cache.php', $active, true ) ) {
3386	return;
3387	}
3388
3389	// Explicitly opt this response OUT of LSCache so the server can't
3390	// shadow our static-rewrite cache with its own internal copy.
3391	header( 'X-LiteSpeed-Cache-Control: no-cache' );
3392	}
3393
3394	/**
3395	* Restore the drop-in + WP_CACHE constant for a site that had caching
3396	* ON before this activation — and ONLY for such a site.
3397	*
3398	* WordPress runs an upgrade as deactivate → wipe plugin files →
3399	* install → activate. The wipe takes advanced-cache.php with it, so
3400	* without this the site serves 100% uncached from the moment the
3401	* update finishes until the next authenticated wp-admin page load
3402	* (auto_heal() is on admin_init). On a site whose admin logs in
3403	* rarely that window is hours or days of silent cache loss, while
3404	* the dashboard still reports cache_enabled = true. (FBS field
3405	* report against 1.1.2 / Pro 1.0.5.)
3406	*
3407	* The `cache_enabled` guard is the whole contract: a FRESH install
3408	* has the option unset, so activation writes nothing and the user
3409	* still opts in explicitly through Cache::toggle() via the
3410	* /cache/toggle REST endpoint. We only ever put back state the user
3411	* already chose — repair, never a new install path. This is what
3412	* keeps us on the right side of the "don't create drop-ins the user
3413	* didn't ask for" guideline while matching what WP Rocket, W3 Total
3414	* Cache and WP Super Cache all do on activation.
3415	*
3416	* @return bool True when a restore was performed.
3417	*/
3418	public static function restore_dropin_if_enabled(): bool {
3419	if ( defined( 'WP_INSTALLING' ) && WP_INSTALLING ) {
3420	return false;
3421	}
3422
3423	// The user's saved choice. Absent/false on a fresh install => no
3424	// drop-in is written and nothing touches wp-config.php.
3425	$opts = get_option( 'xspeed_options', array() );
3426	if ( empty( $opts['cache_enabled'] ) ) {
3427	return false;
3428	}
3429
3430	$restored = false;
3431
3432	// Only (re)install when the drop-in is missing, foreign, or an
3433	// older version of ours — never rewrite a current, healthy file.
3434	$target = WP_CONTENT_DIR . '/advanced-cache.php';
3435	$needs = true;
3436	if ( file_exists( $target ) ) {
3437	$contents = @file_get_contents( $target ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- Best-effort read; a failure just means we reinstall.
3438	if ( is_string( $contents ) && false !== strpos( $contents, 'XSPEED_DROPIN' ) ) {
3439	$source = @file_get_contents( XSPEED_DIR . 'includes/advanced-cache.php' ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- Same.
3440	$needs = self::dropin_version( $contents ) < self::dropin_version( is_string( $source ) ? $source : '' );
3441	}
3442	}
3443	if ( $needs && self::install_dropin() ) {
3444	$restored = true;
3445	}
3446
3447	// WP_CACHE lives in wp-config.php, which the upgrade doesn't touch —
3448	// but a foreign cache plugin or a hand-edit can drop it, and without
3449	// it core never loads the drop-in at all.
3450	if ( ! defined( 'WP_CACHE' ) \|\| ! WP_CACHE ) {
3451	if ( self::set_wp_cache_constant( true ) ) {
3452	$restored = true;
3453	}
3454	}
3455
3456	if ( $restored ) {
3457	Activity_Log::record(
3458	'cache_dropin_restored',
3459	'Cache drop-in restored after a plugin update — caching was already enabled.',
3460	Activity_Log::SUCCESS
3461	);
3462	}
3463
3464	return $restored;
3465	}
3466
3467	/**
3468	* Reconcile drop-in + WP_CACHE + rewrite block with the user's
3469	* saved choice. Runs on admin_init. Cheap when nothing's wrong
3470	* (one option read + a handful of file_exists / defined checks);
3471	* writes only when state has drifted (typical cause: plugin
3472	* upgrade wiped the drop-in, foreign plugin removed our WP_CACHE
3473	* define, or someone hand-edited .htaccess).
3474	*
3475	* Skipped during the WP plugin updater run so we don't race
3476	* the upgrader's own filesystem operations.
3477	*/
3478	public static function auto_heal(): void {
3479	if ( defined( 'WP_INSTALLING' ) && WP_INSTALLING ) {
3480	return;
3481	}
3482	if ( wp_doing_ajax() \|\| wp_doing_cron() ) {
3483	return;
3484	}
3485
3486	$opts = get_option( 'xspeed_options', array() );
3487	if ( empty( $opts['cache_enabled'] ) ) {
3488	return;
3489	}
3490
3491	$dropin_target = WP_CONTENT_DIR . '/advanced-cache.php';
3492	$dropin_ours = false;
3493	$dropin_stale = false;
3494	if ( file_exists( $dropin_target ) ) {
3495	$contents = @file_get_contents( $dropin_target ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
3496	$dropin_ours = is_string( $contents ) && false !== strpos( $contents, 'XSPEED_DROPIN' );
3497	// Reinstall when OUR drop-in is an older version than the source —
3498	// the marker alone can't distinguish an old copy from a new one, so
3499	// a serve-logic change (e.g. the .meta read for 404s/feeds) would
3500	// otherwise never reach existing cache-enabled sites until a manual
3501	// cache toggle. (FBS-82406/82407)
3502	if ( $dropin_ours ) {
3503	$dropin_stale = self::dropin_version( (string) $contents ) < self::dropin_version( @file_get_contents( XSPEED_DIR . 'includes/advanced-cache.php' ) ?: '' ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
3504	}
3505	}
3506
3507	if ( ! $dropin_ours \|\| $dropin_stale ) {
3508	self::install_dropin();
3509	}
3510
3511	if ( ! defined( 'WP_CACHE' ) \|\| ! WP_CACHE ) {
3512	self::set_wp_cache_constant( true );
3513	}
3514
3515	// Rewrite block goes last. It's what turns the static-cache
3516	// tree into a PHP-bypass — every cache hit served by the web
3517	// server directly. Without it we still cache, just at drop-in
3518	// speed (~85ms TTFB) instead of static-file speed (~25-40ms).
3519	//
3520	// Reconcile against mobile_separate: the rewrite is device-blind, so
3521	// it must be ABSENT when mobile_separate is on and PRESENT otherwise.
3522	// auto_heal() runs periodically, so it also repairs a rewrite that
3523	// was left installed before mobile_separate was switched on.
3524	if ( self::static_rewrite_allowed() ) {
3525	if ( ! self::rewrite_installed() ) {
3526	self::install_rewrite();
3527	}
3528	} elseif ( self::rewrite_installed() ) {
3529	self::remove_rewrite();
3530	}
3531
3532	// HITs log file — nginx writes one line per HIT served directly
3533	// (see nginx_snippet()), Cache::get_stats() drains the file via
3534	// Hit_Counter::collect_nginx_log_hits(). If the file vanishes
3535	// (plugin upgrade wiped wp-content/cache/), nginx errors silently
3536	// on the access_log directive and the counter stays at 0.
3537	self::ensure_hits_log_file();
3538	}
3539
3540	/**
3541	* Keep the generic bypass cookie in sync with PHP's caching verdict.
3542	*
3543	* The server config tests exactly one cookie name (Server_Rules::
3544	* BYPASS_COOKIE) forever, and PHP decides what that name means. Adding
3545	* a new excluded cookie therefore needs no config change and no nginx
3546	* reload — the reason this exists.
3547	*
3548	* Session cookie (expiry 0) so it dies with the browser session, and
3549	* deliberately NOT HttpOnly-sensitive: it carries no identity, only the
3550	* boolean "don't serve this visitor a shared cached page".
3551	*
3552	* Honest limit: this can only ever help a visitor PHP has already seen
3553	* once. A bot's first request to a warm page never reaches PHP, which
3554	* is why user-agent rules are still written into the server config
3555	* rather than relying on this.
3556	*
3557	* @param bool $bypass Whether this visitor must skip the cache.
3558	*/
3559	private static function sync_bypass_cookie( bool $bypass ): void {
3560	if ( headers_sent() ) {
3561	return;
3562	}
3563
3564	$name = Server_Rules::BYPASS_COOKIE;
3565	$has = isset( $_COOKIE[ $name ] );
3566
3567	// Only touch the header when the state actually changes — a
3568	// Set-Cookie on every request would make the response uncacheable
3569	// for intermediary caches and add noise to every hit.
3570	if ( $bypass === $has ) {
3571	return;
3572	}
3573
3574	$path = defined( 'COOKIEPATH' ) && COOKIEPATH ? COOKIEPATH : '/';
3575	$domain = defined( 'COOKIE_DOMAIN' ) ? COOKIE_DOMAIN : '';
3576
3577	if ( $bypass ) {
3578	setcookie( $name, '1', 0, $path, (string) $domain, is_ssl(), false );
3579	$_COOKIE[ $name ] = '1';
3580	} else {
3581	setcookie( $name, '', time() - 3600, $path, (string) $domain, is_ssl(), false );
3582	unset( $_COOKIE[ $name ] );
3583	}
3584	}
3585
3586	/**
3587	* Build the .htaccess rules that map cacheable requests to the
3588	* static-cache tree. Conditions are deliberately strict: GET only,
3589	* empty query string, no session/comment-author/post-password
3590	* cookie, and the static file must exist on disk. Anything that
3591	* fails one of these falls through to PHP and the drop-in / full
3592	* WordPress path.
3593	*
3594	* @return string[] Lines for insert_with_markers().
3595	*/
3596	public static function rewrite_block_lines(): array {
3597	// Path relative to ABSPATH so the rule lives in the site-root
3598	// .htaccess regardless of where wp-content sits. WP_CONTENT_DIR
3599	// can be moved, so we compute the document-root-relative form
3600	// at install time and bake it into the rule.
3601	$rel = str_replace( ABSPATH, '/', XSPEED_CACHE_STATIC_DIR );
3602	$rel = '/' . ltrim( $rel, '/' );
3603	$rel = rtrim( $rel, '/' );
3604
3605	// Cookie + user-agent exclusions generated from the live settings.
3606	// See the matching block in nginx_snippet() — same generator, same
3607	// floor, so both servers enforce an identical policy. Apache reads
3608	// .htaccess on every request and we already self-heal this file, so
3609	// Apache/LiteSpeed users get the fix on upgrade with no action.
3610	$cache_opts = Settings_Manager::get( 'cache' );
3611	$cookie_rule = Server_Rules::cookie_rule(
3612	is_array( $cache_opts['excluded_cookies'] ?? null ) ? $cache_opts['excluded_cookies'] : array()
3613	);
3614	$ua_rule = Server_Rules::user_agent_rule(
3615	is_array( $cache_opts['bypass_user_agents'] ?? null ) ? $cache_opts['bypass_user_agents'] : array()
3616	);
3617
3618	$lines = array(
3619	'<IfModule mod_rewrite.c>',
3620	' RewriteEngine On',
3621	' RewriteCond %{REQUEST_METHOD} ^GET$',
3622	' RewriteCond %{QUERY_STRING} ^$',
3623	' RewriteCond %{HTTP_COOKIE} !(' . $cookie_rule['regex'] . ') [NC]',
3624	);
3625
3626	// Only emit the UA condition when there's something to match —
3627	// `!()` would negate an always-true empty match and refuse every
3628	// request, silently disabling the static path.
3629	if ( '' !== $ua_rule['regex'] ) {
3630	// Quoted, because RewriteCond is whitespace-delimited and real
3631	// user-agent fragments contain spaces ("Mozilla/5.0 (compatible").
3632	// Unquoted, a space adds an argument and Apache answers every
3633	// request with a 500 — and because .htaccess is parsed per
3634	// request, `httpd -t` still reports Syntax OK. Server_Rules has
3635	// already excluded quotes and backslashes from the alternation,
3636	// so the closing quote here cannot be escaped away.
3637	$lines[] = ' RewriteCond %{HTTP_USER_AGENT} "!(' . $ua_rule['regex'] . ')" [NC]';
3638	}
3639
3640	return array_merge(
3641	$lines,
3642	array(
3643	// Capture REQUEST_URI without its trailing slash into %1.
3644	// store_static() writes `{host}{uri-without-trailing-slash}/index.html`,
3645	// so this normalization lets `/blog/` and `/blog` both hit
3646	// the same cache file without producing the double-slash
3647	// path that would skip the -f check below.
3648	' RewriteCond %{REQUEST_URI} ^(.*?)/?$',
3649	' RewriteCond %{DOCUMENT_ROOT}' . $rel . '/%{HTTP_HOST}%1/index.html -f',
3650	// Pattern is `^`, NOT `.`. The per-directory rewrite engine
3651	// strips the leading slash before matching, so the HOMEPAGE
3652	// request `/` arrives here as an EMPTY path. `.` requires at
3653	// least one character and therefore never matches the homepage
3654	// — on LiteSpeed (which honors this strictly) the front page
3655	// fell through to PHP while every inner page rewrote fine.
3656	// `^` matches the empty string AND any non-empty path, so it
3657	// covers `/` and `/blog` alike. (Confirmed on OpenLiteSpeed
3658	// 1.8: `.` → homepage served by PHP drop-in; `^` → served
3659	// directly from the static file.)
3660	' RewriteRule ^ ' . $rel . '/%{HTTP_HOST}%1/index.html [L]',
3661	'</IfModule>',
3662	// Mark the statically-served response as a cache HIT.
3663	//
3664	// A file served by the rewrite above bypasses PHP entirely, so
3665	// this directive is the ONLY thing that can identify it as
3666	// cached — both for the user reading response headers and for
3667	// Hit_Counter, which reconciles static hits from the access
3668	// log. Without it the cache works perfectly and reports a 0%
3669	// hit ratio, which reads as "the plugin is broken". (Field
3670	// report against 1.1.2: homepage served byte-identical from
3671	// the static tree, no X-XSpeed-Cache header on any response.)
3672	//
3673	// `always` so the header is set on the 200 from the rewritten
3674	// file, not only on the successful-response table. The
3675	// <IfModule> guard keeps a server without mod_headers from
3676	// 500ing on an unknown directive — on such a host the header
3677	// is silently dropped, which is exactly why
3678	// static_rewrite_allowed() refuses the static path there and
3679	// routes hits through the drop-in instead.
3680	'<IfModule mod_headers.c>',
3681	' <FilesMatch "\\.html$">',
3682	' Header always set X-XSpeed-Cache "HIT (static)"',
3683	' </FilesMatch>',
3684	'</IfModule>',
3685	)
3686	);
3687	}
3688
3689	/**
3690	* Active probe that confirms the web-server static-rewrite path is
3691	* actually serving cached files. Writes a probe file with a random
3692	* nonce, fetches it over HTTP at its public URL, and checks whether
3693	* the response was served directly by the web server (Last-Modified
3694	* + ETag headers + no X-Powered-By: PHP).
3695	*
3696	* Server-agnostic: same probe works for nginx (snippet pasted) and
3697	* Apache / LiteSpeed (.htaccess block installed). If the rewrite
3698	* isn't engaged, the request falls through to WordPress and PHP
3699	* adds its own headers, which the probe detects and reports.
3700	*
3701	* Throttled via a 5-minute transient — we never want this running
3702	* on every Health card paint.
3703	*
3704	* @return array{active:bool, reason:string, code?:int, php?:bool, expires?:int}
3705	*/
3706	/**
3707	* @param bool $allow_probe When false (the default), return ONLY a cached
3708	* result and never make an HTTP request — so admin page loads are never
3709	* blocked by the loopback probe. The actual HTTP probe only runs when a
3710	* caller explicitly opts in (the Health tab / cron). Previously this ran
3711	* synchronously on every dashboard bootstrap, so a slow/timing-out
3712	* loopback request added up to `timeout` seconds to admin page loads on
3713	* hosts that block self-requests. (FBS-82142)
3714	*/
3715	/**
3716	* Discard the cached probe result and run a fresh one.
3717	*
3718	* Without this there was no way to re-check: the result sat in a transient
3719	* for five minutes and nothing ever deleted it, so a user who fixed their
3720	* nginx config kept seeing "nginx detected — configure for max cache speed"
3721	* with no means of confirming the fix worked. (FBS-84012)
3722	*/
3723	public static function recheck_static_rewrite(): array {
3724	delete_transient( 'xspeed_rewrite_probe' );
3725	return self::probe_static_rewrite( true );
3726	}
3727
3728	public static function probe_static_rewrite( bool $allow_probe = false ): array {
3729	$cached = get_transient( 'xspeed_rewrite_probe' );
3730	if ( is_array( $cached ) ) {
3731	return $cached;
3732	}
3733	// No cached result yet and the caller doesn't want to pay for a live
3734	// HTTP probe (e.g. the admin bootstrap): report "pending" without
3735	// blocking. The Health tab will run the real probe on demand.
3736	if ( ! $allow_probe ) {
3737	return array( 'active' => false, 'reason' => 'probe pending', 'pending' => true );
3738	}
3739
3740	$home = home_url( '/' );
3741	$host = (string) wp_parse_url( $home, PHP_URL_HOST );
3742	if ( '' === $host ) {
3743	$result = array( 'active' => false, 'reason' => 'home_url has no host' );
3744	set_transient( 'xspeed_rewrite_probe', $result, MINUTE_IN_SECONDS );
3745	return $result;
3746	}
3747
3748	// Use a randomised path AND nonce so a stale CDN cache entry
3749	// from a prior probe can never make a broken install look
3750	// healthy. Path is namespaced under __xspeed_probe__ so the
3751	// directory listing stays obvious if cleanup misfires.
3752	$slug = wp_generate_password( 12, false, false );
3753	$nonce = wp_generate_password( 24, false, false );
3754	$probe_dir = XSPEED_CACHE_STATIC_DIR . '/' . $host . '/__xspeed_probe__/' . $slug;
3755	$probe_file = $probe_dir . '/index.html';
3756	$probe_url = trailingslashit( $home ) . '__xspeed_probe__/' . $slug . '/';
3757
3758	if ( ! file_exists( $probe_dir ) ) {
3759	wp_mkdir_p( $probe_dir );
3760	}
3761	if ( ! is_dir( $probe_dir ) ) {
3762	$result = array( 'active' => false, 'reason' => 'cannot create probe dir' );
3763	set_transient( 'xspeed_rewrite_probe', $result, MINUTE_IN_SECONDS );
3764	return $result;
3765	}
3766	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents -- WP_Filesystem requires admin credentials we may not have here; the file is in our own cache dir.
3767	file_put_contents( $probe_file, $nonce, LOCK_EX );
3768
3769	// Verify TLS by default — disabling it site-wide is a needless MITM
3770	// exposure (FBS-82142). Only relax verification in local/dev
3771	// environments, where self-signed certs are common and there's no
3772	// real attacker in the loop.
3773	$is_local = function_exists( 'wp_get_environment_type' )
3774	&& in_array( wp_get_environment_type(), array( 'local', 'development' ), true );
3775	$resp = wp_remote_get(
3776	$probe_url,
3777	array(
3778	// 3s cap so a host that hangs on loopback self-requests can't
3779	// stall the caller for long; the result/error is cached so we
3780	// don't repeat the wait every minute.
3781	'timeout' => 3,
3782	'sslverify' => ! $is_local,
3783	'redirection' => 0,
3784	'headers' => array( 'Cache-Control' => 'no-cache' ),
3785	)
3786	);
3787
3788	// Best-effort cleanup so we don't accumulate probe dirs even
3789	// if subsequent calls all hit the transient.
3790	if ( file_exists( $probe_file ) ) {
3791	wp_delete_file( $probe_file );
3792	}
3793	if ( is_dir( $probe_dir ) ) {
3794	// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged, WordPress.WP.AlternativeFunctions.file_system_operations_rmdir -- Best-effort probe-dir cleanup; WP_Filesystem needs admin credentials we don't have here.
3795	@rmdir( $probe_dir );
3796	}
3797
3798	if ( is_wp_error( $resp ) ) {
3799	$result = array(
3800	'active' => false,
3801	// The request never completed, so we learned NOTHING about the
3802	// rewrite. Flagged inconclusive so the UI doesn't tell the user
3803	// to configure a server that may already be configured — a
3804	// blocked loopback, a self-signed cert, or a timeout is a probe
3805	// failure, not a missing rewrite. (FBS-84012)
3806	'inconclusive' => true,
3807	'reason' => 'http error: ' . $resp->get_error_message(),
3808	);
3809	// Cache the failure for the full 5 minutes (not 1) so a host that
3810	// times out on the loopback probe isn't re-probed — and re-stalled
3811	// — on every page load within the window. (FBS-82142)
3812	set_transient( 'xspeed_rewrite_probe', $result, 5 * MINUTE_IN_SECONDS );
3813	return $result;
3814	}
3815
3816	$code = (int) wp_remote_retrieve_response_code( $resp );
3817	$body = (string) wp_remote_retrieve_body( $resp );
3818	$ua_php = '' !== (string) wp_remote_retrieve_header( $resp, 'x-powered-by' );
3819	$has_etag = '' !== (string) wp_remote_retrieve_header( $resp, 'etag' )
3820	\|\| '' !== (string) wp_remote_retrieve_header( $resp, 'last-modified' );
3821	$match = trim( $body ) === $nonce;
3822
3823	// "Active" = the web server served our raw nonce bytes back
3824	// AND emitted the static-serve markers (ETag / Last-Modified)
3825	// AND didn't add an X-Powered-By: PHP header. All three are
3826	// individually noisy; together they're conclusive.
3827	$active = $match && $has_etag && ! $ua_php && 200 === $code;
3828
3829	/*
3830	* `inconclusive` separates "we proved the rewrite isn't serving" from
3831	* "the probe couldn't tell". Only the former should drive a
3832	* configure-your-server banner; the latter previously rendered the
3833	* same alarming copy at a user who had already configured nginx
3834	* correctly, and there was no way to clear it. (FBS-84012)
3835	*/
3836	$inconclusive = false;
3837	if ( $active ) {
3838	$reason = 'static-served';
3839	} elseif ( 200 === $code && $match && $ua_php ) {
3840	$reason = 'php served the file instead of nginx/Apache (rewrite block missing)';
3841	} elseif ( 200 === $code && ! $match ) {
3842	// Something answered 200 with content that isn't our nonce — a CDN,
3843	// a proxy, a security plugin. That tells us nothing about the
3844	// origin's rewrite.
3845	$reason = 'unexpected body (CDN cached an older response?)';
3846	$inconclusive = true;
3847	} elseif ( 404 === $code ) {
3848	$reason = 'probe URL returned 404 (rewrite block missing or wrong path)';
3849	} else {
3850	// Redirects, 403s from a WAF, 5xx — the probe never reached a
3851	// verdict about the rewrite itself.
3852	$reason = sprintf( 'unexpected response (HTTP %d, body %d B, php=%s)', $code, strlen( $body ), $ua_php ? 'yes' : 'no' );
3853	$inconclusive = true;
3854	}
3855
3856	$result = array(
3857	'active' => $active,
3858	'inconclusive' => $inconclusive,
3859	'reason' => $reason,
3860	'code' => $code,
3861	'php' => $ua_php,
3862	);
3863	set_transient( 'xspeed_rewrite_probe', $result, 5 * MINUTE_IN_SECONDS );
3864	return $result;
3865	}
3866
3867	public static function rewrite_installed(): bool {
3868	$htaccess = ABSPATH . '.htaccess';
3869	if ( ! file_exists( $htaccess ) ) {
3870	return false;
3871	}
3872	$existing = @file_get_contents( $htaccess ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
3873	if ( ! is_string( $existing ) ) {
3874	return false;
3875	}
3876	return false !== strpos( $existing, '# BEGIN xSpeed Static Cache' );
3877	}
3878
3879	/**
3880	* Install the static-cache rewrite block at the TOP of .htaccess.
3881	*
3882	* Position matters: WordPress's own block ends with
3883	* `RewriteRule . /index.php [L]` which routes every non-file
3884	* request to PHP. The [L] flag stops the current rewrite pass,
3885	* but Apache restarts the cycle; on the second pass REQUEST_URI
3886	* is /index.php and no static-file check can match. The only
3887	* reliable position for a "serve static if it exists" rule is
3888	* before WordPress's block.
3889	*
3890	* WP's insert_with_markers() always appends, so we manage the
3891	* block manually: strip any prior xSpeed Static Cache markers,
3892	* then write our block followed by the rest of the file.
3893	*/
3894	public static function install_rewrite(): bool {
3895	// The static rewrite is device-blind; never install it when
3896	// mobile_separate is on (see static_rewrite_allowed()).
3897	if ( ! self::static_rewrite_allowed() ) {
3898	return false;
3899	}
3900	$htaccess = ABSPATH . '.htaccess';
3901	$existing = file_exists( $htaccess ) ? @file_get_contents( $htaccess ) : ''; // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
3902	if ( false === $existing ) {
3903	$existing = '';
3904	}
3905	// Apache/LiteSpeed only. nginx hosts: rule won't fire, drop-in
3906	// covers; we skip the write so we don't litter their root.
3907	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_is_writable -- Pre-flight check before file_put_contents; WP_Filesystem requires admin credentials we don't have inside a manage_options REST request.
3908	if ( file_exists( $htaccess ) && ! is_writable( $htaccess ) ) {
3909	return false;
3910	}
3911	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_is_writable -- See above.
3912	if ( ! file_exists( $htaccess ) && ! is_writable( ABSPATH ) ) {
3913	return false;
3914	}
3915
3916	$cleaned = self::strip_marker_block( $existing, 'xSpeed Static Cache' );
3917	$block = self::marker_block( 'xSpeed Static Cache', self::rewrite_block_lines() );
3918	$next = $block . ( '' === $cleaned ? '' : "\n" . $cleaned );
3919
3920	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents, PluginCheck.CodeAnalysis.WriteFile.ABSPATHDetected -- WP_Filesystem requires admin credentials we don't have here; toggle() runs in a REST request authorized by manage_options nonce. The target is the site's .htaccess (configuration file managed by WP core itself), not user data — wp_upload_dir() doesn't apply.
3921	return false !== file_put_contents( $htaccess, $next, LOCK_EX );
3922	}
3923
3924	/**
3925	* Rewrite the .htaccess block in place when — and only when — one is
3926	* already installed.
3927	*
3928	* The block embeds the generated cookie / user-agent exclusion rules,
3929	* so it goes stale the moment those settings change. install_rewrite()
3930	* regenerates it from the live settings, but calling that unconditionally
3931	* on every save would CREATE a block on sites that never enabled the
3932	* static path — silently turning on server-level serving nobody asked
3933	* for. So we refresh only what's already there.
3934	*
3935	* @return bool True when a block was present and rewritten.
3936	*/
3937	public static function refresh_rewrite_if_installed(): bool {
3938	$htaccess = ABSPATH . '.htaccess';
3939	if ( ! file_exists( $htaccess ) ) {
3940	return false;
3941	}
3942	$existing = @file_get_contents( $htaccess ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- Best-effort read; an unreadable file simply means nothing to refresh.
3943	if ( ! is_string( $existing ) \|\| false === strpos( $existing, '# BEGIN xSpeed Static Cache' ) ) {
3944	return false;
3945	}
3946	return self::install_rewrite();
3947	}
3948
3949	public static function remove_rewrite(): bool {
3950	$htaccess = ABSPATH . '.htaccess';
3951	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_is_writable -- See install_rewrite() rationale.
3952	if ( ! file_exists( $htaccess ) \|\| ! is_writable( $htaccess ) ) {
3953	return false;
3954	}
3955	$existing = @file_get_contents( $htaccess ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
3956	if ( false === $existing ) {
3957	return false;
3958	}
3959	$cleaned = self::strip_marker_block( $existing, 'xSpeed Static Cache' );
3960	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents, PluginCheck.CodeAnalysis.WriteFile.ABSPATHDetected -- See install_rewrite() rationale.
3961	return false !== file_put_contents( $htaccess, $cleaned, LOCK_EX );
3962	}
3963
3964	/**
3965	* Strip a `# BEGIN <marker>` ... `# END <marker>` block from a
3966	* .htaccess-style file, including any blank line that immediately
3967	* follows it. Idempotent — returns the input unchanged if the
3968	* marker isn't present.
3969	*/
3970	private static function strip_marker_block( string $contents, string $marker ): string {
3971	$pattern = '/# BEGIN ' . preg_quote( $marker, '/' ) . '\b.?# END ' . preg_quote( $marker, '/' ) . "\b[^\n]\n?\n?/s";
3972	$out = preg_replace( $pattern, '', $contents );
3973	return is_string( $out ) ? $out : $contents;
3974	}
3975
3976	private static function marker_block( string $marker, array $lines ): string {
3977	$header = "# BEGIN $marker\n";
3978	$header .= "# The directives (lines) between \"BEGIN $marker\" and \"END $marker\" are\n";
3979	$header .= "# dynamically generated, and should only be modified via WordPress filters.\n";
3980	$header .= "# Any changes to the directives between these markers will be overwritten.\n";
3981	$footer = "# END $marker\n";
3982	return $header . implode( "\n", $lines ) . "\n" . $footer;
3983	}
3984
3985	/**
3986	* Parse the `XSPEED_DROPIN_VERSION: N` stamp out of a drop-in's source.
3987	* Returns 0 when absent (an un-stamped older copy reinstalls). Used to
3988	* detect a stale installed drop-in vs the bundled source.
3989	*/
3990	private static function dropin_version( string $contents ): int {
3991	if ( preg_match( '/XSPEED_DROPIN_VERSION:\s*(\d+)/', $contents, $m ) ) {
3992	return (int) $m[1];
3993	}
3994	return 0;
3995	}
3996
3997	public static function install_dropin() {
3998	$source = XSPEED_DIR . 'includes/advanced-cache.php';
3999	$target = WP_CONTENT_DIR . '/advanced-cache.php';
4000	if ( ! file_exists( $source ) ) {
4001	return false;
4002	}
4003
4004	global $wp_filesystem;
4005	if ( ! function_exists( 'WP_Filesystem' ) ) {
4006	require_once ABSPATH . 'wp-admin/includes/file.php';
4007	}
4008	WP_Filesystem();
4009	if ( ! $wp_filesystem ) {
4010	return false;
4011	}
4012
4013	$source_contents = $wp_filesystem->get_contents( $source );
4014	if ( ! is_string( $source_contents ) ) {
4015	return false;
4016	}
4017
4018	// Bake the absolute hit-log path into the drop-in. It runs before
4019	// WordPress loads, so it can't resolve wp_upload_dir() itself — we
4020	// substitute the @@XSPEED_HITS_LOG@@ token with the real uploads path
4021	// (never the cache dir; see hits_log_dir() / FBS-82478). Use a single
4022	// quoted PHP string literal so the installed file stays valid PHP.
4023	$source_contents = str_replace(
4024	'@@XSPEED_HITS_LOG@@',
4025	str_replace( "'", "\\'", self::hits_log_path() ),
4026	$source_contents
4027	);
4028
4029	// Bake the cookie + user-agent exclusion rules in too. The drop-in
4030	// runs before WordPress loads, so it cannot read the settings — and
4031	// without them it served the shared anonymous page to any visitor
4032	// PHP had not yet seen (a first-time cart visitor, a bypassed bot).
4033	// The generic bypass cookie only covers repeat visitors; these two
4034	// regexes are what make the FIRST request correct.
4035	//
4036	// Both are already fully escaped by Server_Rules, and each is
4037	// embedded as a single-quoted PHP literal, so a settings value can
4038	// neither break the drop-in's syntax nor execute.
4039	$cache_opts = Settings_Manager::get( 'cache' );
4040	$cookie_rule = Server_Rules::cookie_rule(
4041	is_array( $cache_opts['excluded_cookies'] ?? null ) ? $cache_opts['excluded_cookies'] : array()
4042	);
4043	$ua_rule = Server_Rules::user_agent_rule(
4044	is_array( $cache_opts['bypass_user_agents'] ?? null ) ? $cache_opts['bypass_user_agents'] : array()
4045	);
4046
4047	$source_contents = str_replace(
4048	'@@XSPEED_COOKIE_RE@@',
4049	str_replace( "'", "\\'", $cookie_rule['regex'] ),
4050	$source_contents
4051	);
4052	$source_contents = str_replace(
4053	'@@XSPEED_UA_RE@@',
4054	str_replace( "'", "\\'", $ua_rule['regex'] ),
4055	$source_contents
4056	);
4057
4058	if ( file_exists( $target ) ) {
4059	$existing = $wp_filesystem->get_contents( $target );
4060	$is_xspeed = is_string( $existing ) && false !== strpos( $existing, 'XSPEED_DROPIN' );
4061
4062	if ( $is_xspeed ) {
4063	if ( $existing === $source_contents ) {
4064	return true;
4065	}
4066	return (bool) $wp_filesystem->put_contents( $target, $source_contents, FS_CHMOD_FILE );
4067	}
4068
4069	// Foreign drop-in (e.g. left over from another cache plugin) — back it up
4070	// before overwriting so the user can recover if needed. Uploads dir
4071	// (not wp-content root) keeps the backup out of WordPress's reserved
4072	// drop-in location.
4073	$upload = wp_upload_dir( null, false );
4074	$basedir = isset( $upload['basedir'] ) ? trailingslashit( $upload['basedir'] ) . 'xspeed-backups' : false;
4075	if ( $basedir ) {
4076	if ( ! file_exists( $basedir ) ) {
4077	wp_mkdir_p( $basedir );
4078	self::write_silence( $basedir );
4079	}
4080	$backup = $basedir . '/advanced-cache.foreign-' . gmdate( 'Ymd-His' ) . '.php.bak';
4081	$wp_filesystem->move( $target, $backup, true );
4082	} else {
4083	$wp_filesystem->delete( $target );
4084	}
4085	}
4086
4087	return (bool) $wp_filesystem->put_contents( $target, $source_contents, FS_CHMOD_FILE );
4088	}
4089
4090	public static function remove_dropin() {
4091	$target = WP_CONTENT_DIR . '/advanced-cache.php';
4092	if ( ! file_exists( $target ) ) {
4093	return;
4094	}
4095
4096	global $wp_filesystem;
4097	if ( ! function_exists( 'WP_Filesystem' ) ) {
4098	require_once ABSPATH . 'wp-admin/includes/file.php';
4099	}
4100	WP_Filesystem();
4101	if ( ! $wp_filesystem ) {
4102	return;
4103	}
4104
4105	$contents = $wp_filesystem->get_contents( $target );
4106	if ( is_string( $contents ) && false !== strpos( $contents, 'XSPEED_DROPIN' ) ) {
4107	wp_delete_file( $target );
4108	}
4109	}
4110
4111	/**
4112	* Where wp-config.php actually is.
4113	*
4114	* WordPress core supports the file one directory ABOVE ABSPATH, and
4115	* plenty of installs use that layout. This used to look only in ABSPATH
4116	* and bail, so on those sites the constant could never be written — while
4117	* Health, which did fall back to the parent, reported the file writable
4118	* and told the user to toggle the cache off and on. The advice could
4119	* never work, and its fallback hint ("another plugin left WP_CACHE false
4120	* behind") was wrong too: there was no define at all. (#19, QA on #174)
4121	*
4122	* Returns '' when no wp-config.php can be found in either location.
4123	*/
4124	public static function wp_config_path(): string {
4125	$candidates = array( ABSPATH . 'wp-config.php', dirname( ABSPATH ) . '/wp-config.php' );
4126	foreach ( $candidates as $path ) {
4127	if ( file_exists( $path ) ) {
4128	return $path;
4129	}
4130	}
4131	return '';
4132	}
4133
4134	/**
4135	* Can we actually write the constant right now?
4136	*
4137	* This is the single oracle for that question — Health asks THIS rather
4138	* than running its own `wp_is_writable()` test, so the message a user
4139	* reads can never disagree with what the plugin will do. The two differed
4140	* in both directions: on the path (above) and on the test itself, since
4141	* an FTP/SSH WP_Filesystem transport can refuse a file that
4142	* `wp_is_writable()` reports as writable. (#19, QA on #174)
4143	*/
4144	public static function can_write_wp_config(): bool {
4145	$wp_config = self::wp_config_path();
4146	if ( '' === $wp_config ) {
4147	return false;
4148	}
4149
4150	global $wp_filesystem;
4151	if ( ! function_exists( 'WP_Filesystem' ) ) {
4152	require_once ABSPATH . 'wp-admin/includes/file.php';
4153	}
4154	WP_Filesystem();
4155	return (bool) ( $wp_filesystem && $wp_filesystem->is_writable( $wp_config ) );
4156	}
4157
4158	public static function set_wp_cache_constant( $enable ) {
4159	$wp_config = self::wp_config_path();
4160	if ( '' === $wp_config ) {
4161	return false;
4162	}
4163
4164	global $wp_filesystem;
4165	if ( ! function_exists( 'WP_Filesystem' ) ) {
4166	require_once ABSPATH . 'wp-admin/includes/file.php';
4167	}
4168	WP_Filesystem();
4169	if ( ! $wp_filesystem \|\| ! $wp_filesystem->is_writable( $wp_config ) ) {
4170	return false;
4171	}
4172
4173	$config = $wp_filesystem->get_contents( $wp_config );
4174
4175	if ( $enable ) {
4176	// Own the constant. A previous caching plugin (e.g. WP Rocket sets
4177	// it false on deactivate) can leave `define( 'WP_CACHE', false );`
4178	// behind — presence alone is not enough, the VALUE must be true or
4179	// WordPress never loads advanced-cache.php and our drop-in is dead.
4180	if ( preg_match( "/define\\(\\s['\"]WP_CACHE['\"]\\s,/", $config ) ) {
4181	$rewritten = preg_replace(
4182	"/define\$\\s['\"]WP_CACHE['\"]\\s,\\s[^)]\$\\s*;/",
4183	"define( 'WP_CACHE', true );",
4184	$config,
4185	1
4186	);
4187	// If an existing define was already `true`, the rewrite is a
4188	// no-op string-wise; either way we end on WP_CACHE === true.
4189	if ( null !== $rewritten ) {
4190	$config = $rewritten;
4191	}
4192	} else {
4193	$config = preg_replace( '/(<\?php)/', "$1\ndefine( 'WP_CACHE', true );", $config, 1 );
4194	}
4195	} else {
4196	// Shared with uninstall.php so the two removal paths can't drift
4197	// — they already had, which is why every non-lowercase spelling
4198	// of the value survived a disable. (#9)
4199	require_once XSPEED_DIR . 'includes/wp-cache-constant.php';
4200	$config = xspeed_strip_wp_cache_define( $config );
4201	}
4202
4203	return (bool) $wp_filesystem->put_contents( $wp_config, $config, FS_CHMOD_FILE );
4204	}
4205
4206	/**
4207	* Admin-bar purge menu — a parent node plus one child per visible cache
4208	* type (LiteSpeed-style), instead of a single "Purge All" link. Each
4209	* child posts to the same admin-post handler with its type slug. The
4210	* per-type items only appear for active/licensed modules; "Purge All"
4211	* always shows and always sweeps everything. (FBS-83114)
4212	*
4213	* The parent node links to the settings page rather than a purge URL —
4214	* clicking the top-level item used to wipe the whole cache instantly with
4215	* no confirmation, which is far too destructive for a stray click. Purging
4216	* stays available (and explicit) through the child items. (FBS-84068)
4217	*/
4218	public function admin_bar_purge( $wp_admin_bar ) {
4219	if ( ! current_user_can( 'manage_options' ) ) {
4220	return;
4221	}
4222
4223	$wp_admin_bar->add_node(
4224	array(
4225	'id' => 'xspeed-purge',
4226	'title' => __( 'xSpeed Cache', 'xspeed' ),
4227	'href' => admin_url( 'admin.php?page=' . Admin::PAGE_SLUG ),
4228	)
4229	);
4230
4231	foreach ( self::purge_types() as $slug => $type ) {
4232	if ( empty( $type['visible'] ) ) {
4233	continue;
4234	}
4235	$wp_admin_bar->add_node(
4236	array(
4237	'id' => 'xspeed-purge-' . $slug,
4238	'parent' => 'xspeed-purge',
4239	'title' => esc_html( $type['label'] ),
4240	'href' => self::purge_type_url( $slug ),
4241	)
4242	);
4243	}
4244	}
4245
4246	/**
4247	* Nonce-protected admin-post URL for purging a single type. The nonce
4248	* action is per-type so a leaked URL can't be replayed for a different
4249	* scope.
4250	*/
4251	private static function purge_type_url( string $type ): string {
4252	return wp_nonce_url(
4253	admin_url( 'admin-post.php?action=xspeed_purge&type=' . rawurlencode( $type ) ),
4254	'xspeed_purge_' . $type
4255	);
4256	}
4257
4258	public function handle_admin_bar_purge() {
4259	if ( ! current_user_can( 'manage_options' ) ) {
4260	wp_die( esc_html__( 'Unauthorized.', 'xspeed' ), 403 );
4261	}
4262	$type = isset( $_GET['type'] ) ? sanitize_key( wp_unslash( $_GET['type'] ) ) : 'all';
4263	check_admin_referer( 'xspeed_purge_' . $type );
4264
4265	// Only honour known types; anything else falls back to a full purge.
4266	if ( ! array_key_exists( $type, self::purge_types() ) ) {
4267	$type = 'all';
4268	}
4269	self::purge_type( $type );
4270
4271	wp_safe_redirect( self::safe_purge_redirect( wp_get_referer() ) );
4272	exit;
4273	}
4274
4275	/**
4276	* Resolve a safe redirect target for an admin-bar purge.
4277	*
4278	* The purge sends the admin back where they came from — but the referer
4279	* can be a ONE-SHOT action URL (e.g. update.php?action=upload-plugin from
4280	* installing a plugin zip, or any *.php?action=… that consumed a POST /
4281	* temp upload). Redirecting there re-runs the action with nothing to act
4282	* on, so WordPress dies — the classic "Please select a file" from
4283	* File_Upload_Upgrader. Strip the transient action args so we return to a
4284	* safe, re-GET-able view of the same page; fall back to the dashboard when
4285	* there is no usable referer.
4286	*
4287	* @param string\|false $referer Raw wp_get_referer() value.
4288	* @return string Safe URL to redirect to.
4289	*/
4290	public static function safe_purge_redirect( $referer ): string {
4291	$referer = is_string( $referer ) ? $referer : '';
4292	if ( '' === $referer ) {
4293	return admin_url();
4294	}
4295
4296	// A referer that lands on an action-processing endpoint (update.php,
4297	// update-core.php, plugin/theme install/upload flows) can't be safely
4298	// re-requested — send them to the dashboard instead of replaying it.
4299	$path = (string) wp_parse_url( $referer, PHP_URL_PATH );
4300	if ( preg_match( '#/wp-admin/(update\|update-core)\.php$#', $path ) ) {
4301	return admin_url();
4302	}
4303
4304	// Otherwise keep them on the same page but drop the query args that
4305	// would re-trigger a form action or upload on load.
4306	return remove_query_arg(
4307	array( 'action', 'action2', 'package', 'overwrite', 'plugin', 'theme', 'file', '_wpnonce', '_ajax_nonce' ),
4308	$referer
4309	);
4310	}
4311	}
4312