ezcache / includes / EarlyHints.php

EarlyHints.php in ezCache trunk, at includes/EarlyHints.php

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1	<?php
2	/**
3	* 103 Early Hints
4	*
5	* Sends HTTP 103 Early Hints headers for CSS and JS assets so the browser
6	* can start fetching them before the main response body arrives.
7	*
8	* @package Upress\EzCache
9	*/
10	namespace Upress\EzCache;
11
12	class EarlyHints {
13
14	private static $instance;
15	private $settings;
16
17	/** @var array Collected Link header strings */
18	private $hints = [];
19
20	private function __construct() {
21	$this->settings = Settings::get_settings();
22	}
23
24	public static function instance() {
25	if ( ! self::$instance ) {
26	self::$instance = new self();
27	}
28	return self::$instance;
29	}
30
31	/**
32	* Register WordPress hooks.
33	*/
34	public function register() {
35	if ( empty( $this->settings->enable_early_hints ) ) {
36	return;
37	}
38
39	// Collect enqueued styles and scripts early
40	add_action( 'wp_enqueue_scripts', [ $this, 'collect_assets' ], PHP_INT_MAX );
41
42	// Send Early Hints headers before the page is rendered.
43	// The 'send_headers' hook fires before output — ideal for 103.
44	add_action( 'send_headers', [ $this, 'send_early_hints' ] );
45	}
46
47	/**
48	* Walk through WP's registered styles & scripts and build Link headers.
49	*/
50	public function collect_assets() {
51	global $wp_styles, $wp_scripts;
52
53	if ( $wp_styles instanceof \WP_Styles ) {
54	foreach ( $wp_styles->queue as $handle ) {
55	$dep = $wp_styles->registered[ $handle ] ?? null;
56	if ( $dep && $dep->src ) {
57	$src = $this->normalize_src( $dep->src );
58	if ( $src ) {
59	$this->hints[] = sprintf( '<%s>; rel=preload; as=style', esc_url_raw( $src ) );
60	}
61	}
62	}
63	}
64
65	if ( $wp_scripts instanceof \WP_Scripts ) {
66	foreach ( $wp_scripts->queue as $handle ) {
67	$dep = $wp_scripts->registered[ $handle ] ?? null;
68	if ( $dep && $dep->src ) {
69	$src = $this->normalize_src( $dep->src );
70	if ( $src ) {
71	$this->hints[] = sprintf( '<%s>; rel=preload; as=script', esc_url_raw( $src ) );
72	}
73	}
74	}
75	}
76	}
77
78	/**
79	* Emit 103 Early Hints response headers.
80	*
81	* Note: PHP can only send one status line, so we output the 103 block
82	* via header() calls before WordPress sets the 200. On servers that
83	* buffer (nginx + fastcgi_buffering off or LiteSpeed), this correctly
84	* flushes a 103 interim response first.
85	*/
86	public function send_early_hints() {
87	if ( is_admin() \|\| empty( $this->hints ) ) {
88	return;
89	}
90
91	// Only attempt on servers/PHP versions that support 103
92	if ( ! function_exists( 'header' ) ) {
93	return;
94	}
95
96	// Send 103 header line
97	if ( PHP_MAJOR_VERSION >= 8 && PHP_MINOR_VERSION >= 0 ) {
98	// PHP 8+ header() supports arbitrary status codes without output
99	@header( 'HTTP/1.1 103 Early Hints' );
100	}
101
102	// Deduplicate and send Link headers
103	$seen = [];
104	foreach ( array_unique( $this->hints ) as $hint ) {
105	$key = md5( $hint );
106	if ( isset( $seen[ $key ] ) ) { continue; }
107	$seen[ $key ] = true;
108	@header( 'Link: ' . $hint, false );
109	}
110	}
111
112	/**
113	* Normalize an asset src to an absolute URL, filtering out non-HTTP sources.
114	*
115	* @param string $src
116	* @return string\|false
117	*/
118	private function normalize_src( $src ) {
119	if ( ! $src ) { return false; }
120
121	// Already absolute
122	if ( strpos( $src, 'http' ) === 0 ) {
123	return $src;
124	}
125
126	// Protocol-relative
127	if ( strpos( $src, '//' ) === 0 ) {
128	return ( is_ssl() ? 'https:' : 'http:' ) . $src;
129	}
130
131	// Site-relative
132	if ( strpos( $src, '/' ) === 0 ) {
133	return get_site_url( null, $src );
134	}
135
136	return false;
137	}
138	}
139