function drupal_serve_page_from_cache
drupal_serve_page_from_cache(stdClass $cache)
Sets HTTP headers in preparation for a cached page response.
The headers allow as much as possible in proxies and browsers without any particular knowledge about the pages. Modules can override these headers using drupal_add_http_header().
If the request is conditional (using If-Modified-Since and If-None-Match), and the conditions match those currently in the cache, a 304 Not Modified response is sent.
File
- includes/bootstrap.inc, line 1523
- Functions that need to be loaded on every Drupal request.
Code
function drupal_serve_page_from_cache(stdClass $cache) { // Negotiate whether to use compression. $page_compression = !empty($cache->data['page_compressed']); $return_compressed = $page_compression && isset($_SERVER['HTTP_ACCEPT_ENCODING']) && strpos($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip') !== FALSE; // Get headers set in hook_boot(). Keys are lower-case. $hook_boot_headers = drupal_get_http_header(); // Headers generated in this function, that may be replaced or unset using // drupal_add_http_headers(). Keys are mixed-case. $default_headers = array(); foreach ($cache->data['headers'] as $name => $value) { // In the case of a 304 response, certain headers must be sent, and the // remaining may not (see RFC 2616, section 10.3.5). Do not override // headers set in hook_boot(). $name_lower = strtolower($name); if (in_array($name_lower, array('content-location', 'expires', 'cache-control', 'vary')) && !isset($hook_boot_headers[$name_lower])) { drupal_add_http_header($name, $value); unset($cache->data['headers'][$name]); } } // If the client sent a session cookie, a cached copy will only be served // to that one particular client due to Vary: Cookie. Thus, do not set // max-age > 0, allowing the page to be cached by external proxies, when a // session cookie is present unless the Vary header has been replaced or // unset in hook_boot(). $max_age = !isset($_COOKIE[session_name()]) || isset($hook_boot_headers['vary']) ? variable_get('page_cache_maximum_age', 0) : 0; $default_headers['Cache-Control'] = 'public, max-age=' . $max_age; // Entity tag should change if the output changes. $etag = '"' . $cache->created . '-' . intval($return_compressed) . '"'; header('Etag: ' . $etag); // See if the client has provided the required HTTP headers. $if_modified_since = isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) ? strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) : FALSE; $if_none_match = isset($_SERVER['HTTP_IF_NONE_MATCH']) ? stripslashes($_SERVER['HTTP_IF_NONE_MATCH']) : FALSE; if ($if_modified_since && $if_none_match && $if_none_match == $etag // etag must match && $if_modified_since == $cache->created) { // if-modified-since must match header($_SERVER['SERVER_PROTOCOL'] . ' 304 Not Modified'); drupal_send_headers($default_headers); return; } // Send the remaining headers. foreach ($cache->data['headers'] as $name => $value) { drupal_add_http_header($name, $value); } $default_headers['Last-Modified'] = gmdate(DATE_RFC7231, $cache->created); // HTTP/1.0 proxies does not support the Vary header, so prevent any caching // by sending an Expires date in the past. HTTP/1.1 clients ignores the // Expires header if a Cache-Control: max-age= directive is specified (see RFC // 2616, section 14.9.3). $default_headers['Expires'] = 'Sun, 19 Nov 1978 05:00:00 GMT'; drupal_send_headers($default_headers); // Allow HTTP proxies to cache pages for anonymous users without a session // cookie. The Vary header is used to indicates the set of request-header // fields that fully determines whether a cache is permitted to use the // response to reply to a subsequent request for a given URL without // revalidation. If a Vary header has been set in hook_boot(), it is assumed // that the module knows how to cache the page. if (!isset($hook_boot_headers['vary']) && !variable_get('omit_vary_cookie')) { header('Vary: Cookie'); } if ($page_compression) { header('Vary: Accept-Encoding', FALSE); // If page_compression is enabled, the cache contains gzipped data. if ($return_compressed) { // $cache->data['body'] is already gzip'ed, so make sure // zlib.output_compression does not compress it once more. ini_set('zlib.output_compression', '0'); header('Content-Encoding: gzip'); } else { // The client does not support compression, so unzip the data in the // cache. Strip the gzip header and run uncompress. $cache->data['body'] = gzinflate(substr(substr($cache->data['body'], 10), 0, -8)); } } // Print the page. print $cache->data['body']; }
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https://api.drupal.org/api/drupal/includes!bootstrap.inc/function/drupal_serve_page_from_cache/7.x