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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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/** |
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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 <[email protected]> |
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*/ |
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class HTTP_ConditionalGet |
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{ |
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|
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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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/** |
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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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if ('' !== $spec['encoding']) { |
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$this->_headers['Vary'] = 'Accept-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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/** |
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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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/** |
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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'] = $bytes; |
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} |
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|
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/** |
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* Send headers |
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* |
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* @see getHeaders() |
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* |
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* Note this doesn't "clear" the headers. Calling sendHeaders() will |
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* call header() again (but probably have not effect) and getHeaders() will |
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* still return the headers. |
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* |
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* @return null |
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*/ |
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public function sendHeaders() |
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{ |
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$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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/** |
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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 ($cg->cacheIsValid) { |
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exit(); |
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} |
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} |
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|
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/** |
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* Get a GMT formatted date for use in HTTP headers |
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* |
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* <code> |
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* header('Expires: ' . HTTP_ConditionalGet::gmtdate($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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|
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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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/** |
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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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/** |
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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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/** |
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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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|
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return $isValid; |
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} |
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|
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/** |
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* @return bool |
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*/ |
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protected function resourceMatchedEtag() |
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{ |
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if (!isset($_SERVER['HTTP_IF_NONE_MATCH'])) { |
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return false; |
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} |
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$clientEtagList = PHP_VERSION_ID < 50400 && get_magic_quotes_gpc() |
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? stripslashes($_SERVER['HTTP_IF_NONE_MATCH']) |
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: $_SERVER['HTTP_IF_NONE_MATCH']; |
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$clientEtags = explode(',', $clientEtagList); |
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|
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$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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|
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return true; |
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} |
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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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/** |
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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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{ |
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$etag = trim($etag); |
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|
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return $this->_stripEtag |
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? preg_replace('/;\\w\\w"$/', '"', $etag) |
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: $etag; |
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} |
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|
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/** |
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* @return bool |
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*/ |
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protected function resourceNotModified() |
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{ |
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if (!isset($_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(';', $_SERVER['HTTP_IF_MODIFIED_SINCE'], 2); |
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|
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$date = new DateTime($ifModifiedSince, new DateTimeZone('UTC')); |
| 365 |
|
| 366 |
if ($date->getTimestamp() >= $this->_lmTime) { |
| 367 |
// Apache 2.2's behavior. If there was no ETag match, send the |
| 368 |
// non-encoded version of the ETag value. |
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$this->_headers['ETag'] = $this->normalizeEtag($this->_etag); |
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|
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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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|
