367 lines
12 KiB
PHP
367 lines
12 KiB
PHP
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<?php
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/**
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* Class HTTP_ConditionalGet
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* @package Minify
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* @subpackage HTTP
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*/
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/**
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* Implement conditional GET via a timestamp or hash of content
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*
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* E.g. Content from DB with update time:
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* <code>
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* list($updateTime, $content) = getDbUpdateAndContent();
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* $cg = new HTTP_ConditionalGet(array(
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* 'lastModifiedTime' => $updateTime
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* ,'isPublic' => true
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* ));
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* $cg->sendHeaders();
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* if ($cg->cacheIsValid) {
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* exit();
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* }
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* echo $content;
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* </code>
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*
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* E.g. Shortcut for the above
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* <code>
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* HTTP_ConditionalGet::check($updateTime, true); // exits if client has cache
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* echo $content;
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* </code>
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*
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* E.g. Content from DB with no update time:
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* <code>
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* $content = getContentFromDB();
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* $cg = new HTTP_ConditionalGet(array(
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* 'contentHash' => md5($content)
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* ));
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* $cg->sendHeaders();
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* if ($cg->cacheIsValid) {
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* exit();
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* }
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* echo $content;
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* </code>
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*
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* E.g. Static content with some static includes:
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* <code>
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* // before content
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* $cg = new HTTP_ConditionalGet(array(
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* 'lastUpdateTime' => max(
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* filemtime(__FILE__)
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* ,filemtime('/path/to/header.inc')
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* ,filemtime('/path/to/footer.inc')
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* )
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* ));
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* $cg->sendHeaders();
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* if ($cg->cacheIsValid) {
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* exit();
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* }
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* </code>
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* @package Minify
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* @subpackage HTTP
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* @author Stephen Clay <steve@mrclay.org>
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*/
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class HTTP_ConditionalGet {
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/**
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* Does the client have a valid copy of the requested resource?
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*
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* You'll want to check this after instantiating the object. If true, do
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* not send content, just call sendHeaders() if you haven't already.
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*
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* @var bool
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*/
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public $cacheIsValid = null;
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/**
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* @param array $spec options
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*
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* 'isPublic': (bool) if false, the Cache-Control header will contain
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* "private", allowing only browser caching. (default false)
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*
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* 'lastModifiedTime': (int) if given, both ETag AND Last-Modified headers
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* will be sent with content. This is recommended.
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*
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* 'encoding': (string) if set, the header "Vary: Accept-Encoding" will
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* always be sent and a truncated version of the encoding will be appended
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* to the ETag. E.g. "pub123456;gz". This will also trigger a more lenient
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* checking of the client's If-None-Match header, as the encoding portion of
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* the ETag will be stripped before comparison.
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*
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* 'contentHash': (string) if given, only the ETag header can be sent with
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* content (only HTTP1.1 clients can conditionally GET). The given string
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* should be short with no quote characters and always change when the
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* resource changes (recommend md5()). This is not needed/used if
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* lastModifiedTime is given.
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*
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* 'eTag': (string) if given, this will be used as the ETag header rather
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* than values based on lastModifiedTime or contentHash. Also the encoding
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* string will not be appended to the given value as described above.
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*
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* 'invalidate': (bool) if true, the client cache will be considered invalid
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* without testing. Effectively this disables conditional GET.
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* (default false)
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*
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* 'maxAge': (int) if given, this will set the Cache-Control max-age in
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* seconds, and also set the Expires header to the equivalent GMT date.
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* After the max-age period has passed, the browser will again send a
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* conditional GET to revalidate its cache.
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*/
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public function __construct($spec)
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{
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$scope = (isset($spec['isPublic']) && $spec['isPublic'])
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? 'public'
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: 'private';
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$maxAge = 0;
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// backwards compatibility (can be removed later)
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if (isset($spec['setExpires'])
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&& is_numeric($spec['setExpires'])
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&& ! isset($spec['maxAge'])) {
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$spec['maxAge'] = $spec['setExpires'] - $_SERVER['REQUEST_TIME'];
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}
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if (isset($spec['maxAge'])) {
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$maxAge = $spec['maxAge'];
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$this->_headers['Expires'] = self::gmtDate(
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$_SERVER['REQUEST_TIME'] + $spec['maxAge']
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);
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}
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$etagAppend = '';
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if (isset($spec['encoding'])) {
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$this->_stripEtag = true;
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$this->_headers['Vary'] = 'Accept-Encoding';
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if ('' !== $spec['encoding']) {
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if (0 === strpos($spec['encoding'], 'x-')) {
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$spec['encoding'] = substr($spec['encoding'], 2);
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}
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$etagAppend = ';' . substr($spec['encoding'], 0, 2);
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}
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}
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if (isset($spec['lastModifiedTime'])) {
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$this->_setLastModified($spec['lastModifiedTime']);
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if (isset($spec['eTag'])) { // Use it
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$this->_setEtag($spec['eTag'], $scope);
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} else { // base both headers on time
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$this->_setEtag($spec['lastModifiedTime'] . $etagAppend, $scope);
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}
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} elseif (isset($spec['eTag'])) { // Use it
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$this->_setEtag($spec['eTag'], $scope);
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} elseif (isset($spec['contentHash'])) { // Use the hash as the ETag
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$this->_setEtag($spec['contentHash'] . $etagAppend, $scope);
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}
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$privacy = ($scope === 'private')
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? ', private'
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: '';
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$this->_headers['Cache-Control'] = "max-age={$maxAge}{$privacy}";
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// invalidate cache if disabled, otherwise check
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$this->cacheIsValid = (isset($spec['invalidate']) && $spec['invalidate'])
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? false
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: $this->_isCacheValid();
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}
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/**
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* Get array of output headers to be sent
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*
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* In the case of 304 responses, this array will only contain the response
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* code header: array('_responseCode' => 'HTTP/1.0 304 Not Modified')
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*
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* Otherwise something like:
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* <code>
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* array(
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* 'Cache-Control' => 'max-age=0, public'
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* ,'ETag' => '"foobar"'
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* )
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* </code>
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*
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* @return array
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*/
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public function getHeaders()
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{
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return $this->_headers;
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}
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/**
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* Set the Content-Length header in bytes
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*
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* With most PHP configs, as long as you don't flush() output, this method
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* is not needed and PHP will buffer all output and set Content-Length for
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* you. Otherwise you'll want to call this to let the client know up front.
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*
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* @param int $bytes
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*
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* @return int copy of input $bytes
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*/
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public function setContentLength($bytes)
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{
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return $this->_headers['Content-Length'] = $bytes;
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}
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/**
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* Send headers
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*
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* @see getHeaders()
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*
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* Note this doesn't "clear" the headers. Calling sendHeaders() will
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* call header() again (but probably have not effect) and getHeaders() will
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* still return the headers.
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*
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* @return null
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*/
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public function sendHeaders()
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{
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$headers = $this->_headers;
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if (array_key_exists('_responseCode', $headers)) {
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// FastCGI environments require 3rd arg to header() to be set
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list(, $code) = explode(' ', $headers['_responseCode'], 3);
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header($headers['_responseCode'], true, $code);
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unset($headers['_responseCode']);
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}
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foreach ($headers as $name => $val) {
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header($name . ': ' . $val);
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}
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}
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/**
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* Exit if the client's cache is valid for this resource
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*
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* This is a convenience method for common use of the class
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*
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* @param int $lastModifiedTime if given, both ETag AND Last-Modified headers
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* will be sent with content. This is recommended.
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*
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* @param bool $isPublic (default false) if true, the Cache-Control header
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* will contain "public", allowing proxies to cache the content. Otherwise
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* "private" will be sent, allowing only browser caching.
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*
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* @param array $options (default empty) additional options for constructor
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*/
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public static function check($lastModifiedTime = null, $isPublic = false, $options = array())
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{
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if (null !== $lastModifiedTime) {
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$options['lastModifiedTime'] = (int)$lastModifiedTime;
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}
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$options['isPublic'] = (bool)$isPublic;
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$cg = new HTTP_ConditionalGet($options);
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$cg->sendHeaders();
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if ($cg->cacheIsValid) {
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exit();
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}
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}
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/**
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* Get a GMT formatted date for use in HTTP headers
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*
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* <code>
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* header('Expires: ' . HTTP_ConditionalGet::gmtdate($time));
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* </code>
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*
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* @param int $time unix timestamp
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*
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* @return string
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*/
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public static function gmtDate($time)
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{
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return gmdate('D, d M Y H:i:s \G\M\T', $time);
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}
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protected $_headers = array();
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protected $_lmTime = null;
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protected $_etag = null;
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protected $_stripEtag = false;
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/**
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* @param string $hash
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*
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* @param string $scope
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*/
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protected function _setEtag($hash, $scope)
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{
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$this->_etag = '"' . substr($scope, 0, 3) . $hash . '"';
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$this->_headers['ETag'] = $this->_etag;
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}
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/**
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* @param int $time
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*/
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protected function _setLastModified($time)
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{
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$this->_lmTime = (int)$time;
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$this->_headers['Last-Modified'] = self::gmtDate($time);
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}
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/**
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* Determine validity of client cache and queue 304 header if valid
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*
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* @return bool
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*/
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protected function _isCacheValid()
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{
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if (null === $this->_etag) {
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// lmTime is copied to ETag, so this condition implies that the
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// server sent neither ETag nor Last-Modified, so the client can't
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// possibly has a valid cache.
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return false;
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}
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$isValid = ($this->resourceMatchedEtag() || $this->resourceNotModified());
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if ($isValid) {
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$this->_headers['_responseCode'] = 'HTTP/1.0 304 Not Modified';
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}
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return $isValid;
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}
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/**
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* @return bool
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*/
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protected function resourceMatchedEtag()
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{
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if (!isset($_SERVER['HTTP_IF_NONE_MATCH'])) {
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return false;
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}
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$clientEtagList = get_magic_quotes_gpc()
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? stripslashes($_SERVER['HTTP_IF_NONE_MATCH'])
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: $_SERVER['HTTP_IF_NONE_MATCH'];
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$clientEtags = explode(',', $clientEtagList);
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$compareTo = $this->normalizeEtag($this->_etag);
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foreach ($clientEtags as $clientEtag) {
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if ($this->normalizeEtag($clientEtag) === $compareTo) {
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// respond with the client's matched ETag, even if it's not what
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// we would've sent by default
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$this->_headers['ETag'] = trim($clientEtag);
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return true;
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}
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}
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return false;
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}
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/**
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* @param string $etag
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*
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* @return string
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*/
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protected function normalizeEtag($etag) {
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$etag = trim($etag);
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return $this->_stripEtag
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? preg_replace('/;\\w\\w"$/', '"', $etag)
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: $etag;
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}
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/**
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* @return bool
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*/
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protected function resourceNotModified()
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{
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if (!isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
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return false;
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}
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// strip off IE's extra data (semicolon)
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list($ifModifiedSince) = explode(';', $_SERVER['HTTP_IF_MODIFIED_SINCE'], 2);
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if (strtotime($ifModifiedSince) >= $this->_lmTime) {
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// Apache 2.2's behavior. If there was no ETag match, send the
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// non-encoded version of the ETag value.
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$this->_headers['ETag'] = $this->normalizeEtag($this->_etag);
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return true;
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}
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return false;
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}
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}
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