1 Feb 2001 prenagha   » (Apprentice)

Worked out a server-side caching mechanism for PHP based sites. This is extremely helpful to performance. Somewhat like the concept of a reverse-cache sitting in front of a webserver, like squid, but this can be used on those hosts that don't have that software installed. Here is a snapshot of the PHP code, usage should be self-explanatory. I just started testing it, but so far so good.

function pageCacheStart($ttl=600, $debug=FALSE, 
  $cacheDir='/tmp/pagecache', $sidName='psid') {

//to force the cache OFF, uncomment next line //return FALSE;

// we only use the cache for GET requests. // we don't use the cache for ssl requests. if ($HTTP_SERVER_VARS['REQUEST_METHOD']!='GET' || isset($HTTP_SERVER_VARS['HTTPS']) ) { return FALSE; }


// if we have the sid in the get vars, // and we have the sid in the cookie vars, // then we can act as if the sid is not in the get // vars and return a cached page. // if the sid is in the get, and not as a cookie, // then we don't use a cached version since all the URLs // in the page need to be rewritten with the sid by php. if (isset($HTTP_GET_VARS[$sidName])) { if (isset($HTTP_COOKIE_VARS[$sidName])) { if (count($HTTP_GET_VARS)==1) { $REQUEST_URI = $HTTP_SERVER_VARS['SCRIPT_NAME']; } else { $REQUEST_URI = ereg_replace('&'.$sidName.'=.{32}','',$REQUEST_URI); } } else { return FALSE; } }

// get the hostname if (isset($HTTP_SERVER_VARS['HTTP_HOST'])) { $HOST = $HTTP_SERVER_VARS['HTTP_HOST']; } else { $HOST = $HTTP_SERVER_VARS['SERVER_NAME']; }

// cache directory use for pages from this host. $cacheDirHost = $cacheDir.'/'.strtolower($HOST);

// build the name of the cache file for this page $cacheFile = $cacheDirHost.'/'.md5($REQUEST_URI).'.cache';

$mtime = filemtime($cacheFile); $time = time();

if ($mtime >= ($time - $ttl)) {

//send cache control headers that let client browser //cache the page. header('Expires: '.gmdate('D, d M Y H:i:s', $time + $ttl).' GMT'); header('Last-Modified: '.gmdate('D, d M Y H:i:s', $mtime).' GMT'); header('Cache-Control: public'); header('Cache-Control: max-age='.$ttl);

//get the cached file and send it to the browser immediately readfile($cacheFile);

//debug info if ($debug) { print("<hr>CACHED COPY
filename: $cacheFile\n"); print("
mtime: ".date('m/d/y h:i:s a',filemtime($cacheFile))."\n"); print("
cache age ".(time()-filemtime($cacheFile))." seconds\n"); }

//exit this server session exit();

} else { // the directory existence is the signal that pages // from this host should be cached. if (!is_dir($cacheDirHost)) { return FALSE; }

ob_start(); print("<!-- request: ".$HOST.$REQUEST_URI." -->\n"); return $cacheFile; } }

function pageCacheEnd($cacheFile='', $debug=FALSE) { $html = ob_get_contents(); ob_end_flush();

if (empty($cacheFile)) { } else { if ($debug) { print("<hr>writing new cacheFile: $cacheFile\n"); }

if ($fp = @fopen ($cacheFile, 'w')) { @fwrite ($fp, $html); @fclose ($fp); } } }

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