111 lines
2.7 KiB
PHP
111 lines
2.7 KiB
PHP
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<?php
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/**
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* HTTP caching functions
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*
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* Enable use of HTTP 304 headers for unmodified content to save bandwidth
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*
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* @package Core
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* @author Andreas Götz <cpuidle@gmx.de>
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* @version $Id: httpcache.php,v 1.5 2010/11/05 10:38:47 andig2 Exp $
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*/
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/**
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* Start output buffering
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*/
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function httpCacheCaptureStart()
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{
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ob_start();
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}
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/**
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* Stop output buffering
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*
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* @param string MD5 hash of content
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*/
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function httpCacheCaptureEnd()
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{
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$content = ob_get_contents();
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ob_end_clean();
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return $content;
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}
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/**
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* Get last modified data for given etag
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* Checks session for known etag and timestamp
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*/
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function httpCacheCheckTag($template, $etag)
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{
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if ($etag != $_SESSION['vdb'][$template]['etag'])
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{
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$lastmod = time();
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$_SESSION['vdb'][$template]['etag'] = $etag;
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$_SESSION['vdb'][$template]['time'] = $lastmod;
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}
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else
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{
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$lastmod = $_SESSION['vdb'][$template]['time'];
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}
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return($lastmod);
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}
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/**
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* Output 304 Not Modified header
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* Require browser to re-check on next request
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*/
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function httpCacheHeaders($etag, $expires)
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{
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header(php_sapi_name() == 'cgi' ? 'Status: 304 Not Modified' : 'HTTP/1.x 304 Not Modified');
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header("ETag: {$etag}");
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header("Cache-Control: private, max-age={$expires}, pre-check=0, post-check=0");
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header("Content-Length: 0");
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header("Content-Type: !invalid");
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exit();
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}
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/**
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* Check if output was modified since last request
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* If unmodifed, output 304 Not Modified header
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* Otherwise add additional ETag and LastModified headers
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*/
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function httpCacheOutput($template, $content)
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{
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$etag = '"'.md5($content).'"';
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// check if 'sending' is necessary (using cache functions)
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$sendbody = true;
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$expires = 0;
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$lastmod = httpCacheCheckTag($template, $etag);
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// check 'If-Modified-Since' header
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if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) && gmdate('D, d M Y H:i:s', $lastmod)." GMT" == trim($_SERVER['HTTP_IF_MODIFIED_SINCE']))
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{
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httpCacheHeaders($etag, $expires);
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}
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// check 'If-None-Match' header (ETag)
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if ($sendbody && isset($_SERVER['HTTP_IF_NONE_MATCH']))
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{
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$inm = explode(',', $_SERVER['HTTP_IF_NONE_MATCH']);
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foreach ($inm as $i)
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{
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if (trim($i) != $etag) continue;
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httpCacheHeaders($etag, $expires);
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}
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}
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// send with caching headers (enable cache for one day)
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$exp_gmt = gmdate('D, d M Y H:i:s', time() + $expires).' GMT';
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$mod_gmt = gmdate('D, d M Y H:i:s', $lastmod).' GMT';
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header("Expires: {$exp_gmt}");
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header("Last-Modified: {$mod_gmt}");
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header("Cache-Control: private, max-age={$expires}, pre-check=0, post-check=0");
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header("Pragma: !invalid");
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header("ETag: {$etag}");
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echo $content;
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}
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?>
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