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