webpage caching - php

Question

I am looking for a best solution for caching my webpages example http:/www.website.com/test.php?d=2011-11-01 which has url rewrite rule to become http:/www.website.com/testd-2011-11-01.html
the scripts below does not work for dynamic web page it give the same page regardless of the query.
<?php
$cachefile = "cache/".$reqfilename.".html";
$cachetime = 240 * 60; // 5 minutes
// Serve from the cache if it is younger than $cachetime
if (file_exists($cachefile) && (time() - $cachetime
< filemtime($cachefile)))
{
include($cachefile);
echo "<!-- Cached ".date('jS F Y H:i', filemtime($cachefile))."
-->";
exit;
}
ob_start(); // start the output buffer?>
my website content here
<?php
// open the cache file for writing
$fp = fopen($cachefile, 'w');
// save the contents of output buffer to the file
fwrite($fp, ob_get_contents());
// close the file
fclose($fp);
// Send the output to the browser
ob_end_flush(); ?>

Answer 1

If your URL looks like testd-2011-11-01.html, you have two possible solutions :
Use some RewriteRule, so that URL is rewritten to test.php?d=2011-11-01 ; and, then, your test.php script can deal with the cache generation / invalidation
Or use a cronjob, that will regenerate the testd-2011-11-01.html static file every X minutes.
The first solution is the one that's generally used, as it only requires you to setup a RewriteRule (and those are often available, even on cheap hosting services).
The second solution might be a bit better for performances (no PHP code is ever executed, except when the cronjob runs) ; but the difference is probably not that important, except if you have a very big website with an awful lot of users.

Answer 2

Something like this could work:
class SimpleCache {
private $_cacheDir = '/path/to/cache';
private $_cacheTime = 240*60;
public function isCached( $id ) {
$cacheFilename = $this->_cache . "/" . $id . "_*";
$files = glob($cacheFilename, GLOB_NOSORT);
if( $files && !empty($files) ) {
// There should always be one file in the array
$filename = $files[0];
$params = explode("_", $filename);
$cacheTime = strtok($params[1], '.');
// Check if the cached file is too old
if( time() - $params[1] > $this->_cacheTime ) {
#unlink($filename);
}
else {
return $filename;
}
}
return false;
}
public function cache( $id, $data ) {
$filename = $this->_cache . "/" . $id. "_" . time() . ".cache";
if( !($fp = #fopen($filename, "w")) ) {
return false;
}
if( !#fwrite($fp, $data) ) {
#fclose($fp);
return false;
}
#fclose($fp);
return true;
}
}
$cache = new SimpleCache();
if( !($buffer = $cache->isCached($reqfilename)) ) {
// Produce the contects of the file and save them in the $buffer variable
$cache->cache($reqfilename, $buffer);
}
echo $buffer;
But you could use memcached, APC, and more advanced caching techniques if you are up to it

Answer 3

You can use HTTP caching. You send headers telling the client (browser) to cache the whole page for a certain period of time.
// 5 minutes
header('Cache-Control: max-age=300');
If you have control over your hosting environment, you can also add a reverse proxy like varnish or nginx in front of your webserver. This proxy will then cache these requests for you, making the cached version shared between all visitors of your site.
See also the HTTP/1.1 specification.