wp-super-minify / includes / min / lib / HTTP / ConditionalGet.php

ConditionalGet.php in WP Super Minify • Minify, Compress and Cache HTML, CSS & JavaScript trunk, at includes/min/lib/HTTP/ConditionalGet.php

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1	<?php
2	/**
3	* Class HTTP_ConditionalGet
4	* @package Minify
5	* @subpackage HTTP
6	*/
7
8	/**
9	* Implement conditional GET via a timestamp or hash of content
10	*
11	* E.g. Content from DB with update time:
12	* <code>
13	* list($updateTime, $content) = getDbUpdateAndContent();
14	* $cg = new HTTP_ConditionalGet(array(
15	* 'lastModifiedTime' => $updateTime
16	* ,'isPublic' => true
17	* ));
18	* $cg->sendHeaders();
19	* if ($cg->cacheIsValid) {
20	* exit();
21	* }
22	* echo $content;
23	* </code>
24	*
25	* E.g. Shortcut for the above
26	* <code>
27	* HTTP_ConditionalGet::check($updateTime, true); // exits if client has cache
28	* echo $content;
29	* </code>
30	*
31	* E.g. Content from DB with no update time:
32	* <code>
33	* $content = getContentFromDB();
34	* $cg = new HTTP_ConditionalGet(array(
35	* 'contentHash' => md5($content)
36	* ));
37	* $cg->sendHeaders();
38	* if ($cg->cacheIsValid) {
39	* exit();
40	* }
41	* echo $content;
42	* </code>
43	*
44	* E.g. Static content with some static includes:
45	* <code>
46	* // before content
47	* $cg = new HTTP_ConditionalGet(array(
48	* 'lastUpdateTime' => max(
49	* filemtime(__FILE__)
50	* ,filemtime('/path/to/header.inc')
51	* ,filemtime('/path/to/footer.inc')
52	* )
53	* ));
54	* $cg->sendHeaders();
55	* if ($cg->cacheIsValid) {
56	* exit();
57	* }
58	* </code>
59	* @package Minify
60	* @subpackage HTTP
61	* @author Stephen Clay <steve@mrclay.org>
62	*/
63	class HTTP_ConditionalGet
64	{
65
66	/**
67	* Does the client have a valid copy of the requested resource?
68	*
69	* You'll want to check this after instantiating the object. If true, do
70	* not send content, just call sendHeaders() if you haven't already.
71	*
72	* @var bool
73	*/
74	public $cacheIsValid = null;
75
76	/**
77	* @param array $spec options
78	*
79	* 'isPublic': (bool) if false, the Cache-Control header will contain
80	* "private", allowing only browser caching. (default false)
81	*
82	* 'lastModifiedTime': (int) if given, both ETag AND Last-Modified headers
83	* will be sent with content. This is recommended.
84	*
85	* 'encoding': (string) if set, the header "Vary: Accept-Encoding" will
86	* always be sent and a truncated version of the encoding will be appended
87	* to the ETag. E.g. "pub123456;gz". This will also trigger a more lenient
88	* checking of the client's If-None-Match header, as the encoding portion of
89	* the ETag will be stripped before comparison.
90	*
91	* 'contentHash': (string) if given, only the ETag header can be sent with
92	* content (only HTTP1.1 clients can conditionally GET). The given string
93	* should be short with no quote characters and always change when the
94	* resource changes (recommend md5()). This is not needed/used if
95	* lastModifiedTime is given.
96	*
97	* 'eTag': (string) if given, this will be used as the ETag header rather
98	* than values based on lastModifiedTime or contentHash. Also the encoding
99	* string will not be appended to the given value as described above.
100	*
101	* 'invalidate': (bool) if true, the client cache will be considered invalid
102	* without testing. Effectively this disables conditional GET.
103	* (default false)
104	*
105	* 'maxAge': (int) if given, this will set the Cache-Control max-age in
106	* seconds, and also set the Expires header to the equivalent GMT date.
107	* After the max-age period has passed, the browser will again send a
108	* conditional GET to revalidate its cache.
109	*/
110	public function __construct($spec)
111	{
112	$scope = (isset($spec['isPublic']) && $spec['isPublic'])
113	? 'public'
114	: 'private';
115	$maxAge = 0;
116	// backwards compatibility (can be removed later)
117	if (isset($spec['setExpires'])
118	&& is_numeric($spec['setExpires'])
119	&& ! isset($spec['maxAge'])) {
120	$spec['maxAge'] = $spec['setExpires'] - $_SERVER['REQUEST_TIME'];
121	}
122	if (isset($spec['maxAge'])) {
123	$maxAge = $spec['maxAge'];
124	$this->_headers['Expires'] = self::gmtDate(
125	$_SERVER['REQUEST_TIME'] + $spec['maxAge']
126	);
127	}
128	$etagAppend = '';
129	if (isset($spec['encoding'])) {
130	$this->_stripEtag = true;
131	if ('' !== $spec['encoding']) {
132	$this->_headers['Vary'] = 'Accept-Encoding';
133	if (0 === strpos($spec['encoding'], 'x-')) {
134	$spec['encoding'] = substr($spec['encoding'], 2);
135	}
136	$etagAppend = ';' . substr($spec['encoding'], 0, 2);
137	}
138	}
139	if (isset($spec['lastModifiedTime'])) {
140	$this->_setLastModified($spec['lastModifiedTime']);
141	if (isset($spec['eTag'])) { // Use it
142	$this->_setEtag($spec['eTag'], $scope);
143	} else { // base both headers on time
144	$this->_setEtag($spec['lastModifiedTime'] . $etagAppend, $scope);
145	}
146	} elseif (isset($spec['eTag'])) { // Use it
147	$this->_setEtag($spec['eTag'], $scope);
148	} elseif (isset($spec['contentHash'])) { // Use the hash as the ETag
149	$this->_setEtag($spec['contentHash'] . $etagAppend, $scope);
150	}
151	$privacy = ($scope === 'private')
152	? ', private'
153	: '';
154	$this->_headers['Cache-Control'] = "max-age={$maxAge}{$privacy}";
155	// invalidate cache if disabled, otherwise check
156	$this->cacheIsValid = (isset($spec['invalidate']) && $spec['invalidate'])
157	? false
158	: $this->_isCacheValid();
159	}
160
161	/**
162	* Get array of output headers to be sent
163	*
164	* In the case of 304 responses, this array will only contain the response
165	* code header: array('_responseCode' => 'HTTP/1.0 304 Not Modified')
166	*
167	* Otherwise something like:
168	* <code>
169	* array(
170	* 'Cache-Control' => 'max-age=0, public'
171	* ,'ETag' => '"foobar"'
172	* )
173	* </code>
174	*
175	* @return array
176	*/
177	public function getHeaders()
178	{
179	return $this->_headers;
180	}
181
182	/**
183	* Set the Content-Length header in bytes
184	*
185	* With most PHP configs, as long as you don't flush() output, this method
186	* is not needed and PHP will buffer all output and set Content-Length for
187	* you. Otherwise you'll want to call this to let the client know up front.
188	*
189	* @param int $bytes
190	*
191	* @return int copy of input $bytes
192	*/
193	public function setContentLength($bytes)
194	{
195	return $this->_headers['Content-Length'] = $bytes;
196	}
197
198	/**
199	* Send headers
200	*
201	* @see getHeaders()
202	*
203	* Note this doesn't "clear" the headers. Calling sendHeaders() will
204	* call header() again (but probably have not effect) and getHeaders() will
205	* still return the headers.
206	*
207	* @return null
208	*/
209	public function sendHeaders()
210	{
211	$headers = $this->_headers;
212	if (array_key_exists('_responseCode', $headers)) {
213	// FastCGI environments require 3rd arg to header() to be set
214	list(, $code) = explode(' ', $headers['_responseCode'], 3);
215	header($headers['_responseCode'], true, $code);
216	unset($headers['_responseCode']);
217	}
218	foreach ($headers as $name => $val) {
219	header($name . ': ' . $val);
220	}
221	}
222
223	/**
224	* Exit if the client's cache is valid for this resource
225	*
226	* This is a convenience method for common use of the class
227	*
228	* @param int $lastModifiedTime if given, both ETag AND Last-Modified headers
229	* will be sent with content. This is recommended.
230	*
231	* @param bool $isPublic (default false) if true, the Cache-Control header
232	* will contain "public", allowing proxies to cache the content. Otherwise
233	* "private" will be sent, allowing only browser caching.
234	*
235	* @param array $options (default empty) additional options for constructor
236	*/
237	public static function check($lastModifiedTime = null, $isPublic = false, $options = array())
238	{
239	if (null !== $lastModifiedTime) {
240	$options['lastModifiedTime'] = (int)$lastModifiedTime;
241	}
242	$options['isPublic'] = (bool)$isPublic;
243	$cg = new HTTP_ConditionalGet($options);
244	$cg->sendHeaders();
245	if ($cg->cacheIsValid) {
246	exit();
247	}
248	}
249
250	/**
251	* Get a GMT formatted date for use in HTTP headers
252	*
253	* <code>
254	* header('Expires: ' . HTTP_ConditionalGet::gmtdate($time));
255	* </code>
256	*
257	* @param int $time unix timestamp
258	*
259	* @return string
260	*/
261	public static function gmtDate($time)
262	{
263	return gmdate('D, d M Y H:i:s \G\M\T', $time);
264	}
265
266	protected $_headers = array();
267	protected $_lmTime = null;
268	protected $_etag = null;
269	protected $_stripEtag = false;
270
271	/**
272	* @param string $hash
273	*
274	* @param string $scope
275	*/
276	protected function _setEtag($hash, $scope)
277	{
278	$this->_etag = '"' . substr($scope, 0, 3) . $hash . '"';
279	$this->_headers['ETag'] = $this->_etag;
280	}
281
282	/**
283	* @param int $time
284	*/
285	protected function _setLastModified($time)
286	{
287	$this->_lmTime = (int)$time;
288	$this->_headers['Last-Modified'] = self::gmtDate($time);
289	}
290
291	/**
292	* Determine validity of client cache and queue 304 header if valid
293	*
294	* @return bool
295	*/
296	protected function _isCacheValid()
297	{
298	if (null === $this->_etag) {
299	// lmTime is copied to ETag, so this condition implies that the
300	// server sent neither ETag nor Last-Modified, so the client can't
301	// possibly has a valid cache.
302	return false;
303	}
304	$isValid = ($this->resourceMatchedEtag() \|\| $this->resourceNotModified());
305	if ($isValid) {
306	$this->_headers['_responseCode'] = 'HTTP/1.0 304 Not Modified';
307	}
308
309	return $isValid;
310	}
311
312	/**
313	* @return bool
314	*/
315	protected function resourceMatchedEtag()
316	{
317	if (!isset($_SERVER['HTTP_IF_NONE_MATCH'])) {
318	return false;
319	}
320	$clientEtagList = PHP_VERSION_ID < 50400 && get_magic_quotes_gpc()
321	? stripslashes($_SERVER['HTTP_IF_NONE_MATCH'])
322	: $_SERVER['HTTP_IF_NONE_MATCH'];
323	$clientEtags = explode(',', $clientEtagList);
324
325	$compareTo = $this->normalizeEtag($this->_etag);
326	foreach ($clientEtags as $clientEtag) {
327	if ($this->normalizeEtag($clientEtag) === $compareTo) {
328	// respond with the client's matched ETag, even if it's not what
329	// we would've sent by default
330	$this->_headers['ETag'] = trim($clientEtag);
331
332	return true;
333	}
334	}
335
336	return false;
337	}
338
339	/**
340	* @param string $etag
341	*
342	* @return string
343	*/
344	protected function normalizeEtag($etag)
345	{
346	$etag = trim($etag);
347
348	return $this->_stripEtag
349	? preg_replace('/;\\w\\w"$/', '"', $etag)
350	: $etag;
351	}
352
353	/**
354	* @return bool
355	*/
356	protected function resourceNotModified()
357	{
358	if (!isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
359	return false;
360	}
361	// strip off IE's extra data (semicolon)
362	list($ifModifiedSince) = explode(';', $_SERVER['HTTP_IF_MODIFIED_SINCE'], 2);
363
364	$date = new DateTime($ifModifiedSince, new DateTimeZone('UTC'));
365
366	if ($date->getTimestamp() >= $this->_lmTime) {
367	// Apache 2.2's behavior. If there was no ETag match, send the
368	// non-encoded version of the ETag value.
369	$this->_headers['ETag'] = $this->normalizeEtag($this->_etag);
370
371	return true;
372	}
373
374	return false;
375	}
376	}
377