» Benchmark: $gentime vs. filemtime (Filecache)

<?php
/*
	// version 1
	// run: 0.247105841635
	// run: 0.261900234224 refresh set to 10 seconds
	// run: 0.256287105084 refresh set to 10 seconds
	// run: [b]0.249131891729[/b] refresh set to 30 seconds
	// fastest run: 0.104637145996
	// run: 0.234740469457 without refresh
	// fastest run: 0.0934660434723
	// run: 0.237568306923 without refresh / without clearstatcache()
	// fastest run: 0.147907018661
	$gentime = 0;
	$data = array();
	// cache file will be included if it exists
	if (file_exists($filename)) {
		include($filename);
	}
	// cache file will be created if didn't existed or refreshed all 2 seconds
	if (!$data || $gentime + 86400 < $now) {
		// read data (db query...)
		$data = array(
			'id' => 1111,
			0 => 'long text',
			1 => 'long text',
			2 => 'long text with quotes',
		);
		// write cache file
		// it is necessary to lock first and truncate afterwards to avoid including a 
		// partial php file (won't work in 100% of all cases as it is still possible 
		// to include it after truncating it!)
		$h = @fopen($filename, 'a');
		@flock($h, LOCK_EX);
		@ftruncate($h, 0);
		@fwrite($h, '<' . '?php $gentime = ' . $now . '; $data = unserialize(\'' . str_replace(array('\\', '\''), array('\\\\', '\\\''), serialize($data)) . '\'); ?' . '>');
		@flock($h, LOCK_UN);
		@fclose($h);
		@umask(0000);
		@chmod($filename, 0644);
	}
	// only for the benchmark to avoid caching
	clearstatcache();
*/
/*
	// version 2
	// run: 0.217099111083
	// run: 0.222138965129
	// run: 0.220421209337 refresh set to 10 seconds
	// run: [b]0.222239365575[/b] refresh set to 30 seconds
	// run: 0.219991838929 without refresh
	// fastest run: 0.0898759365082
	// run: 0.181516561508 without refresh / without clearstatcache()
	// fastest run: 0.103751897812
	$data = array();
	// cache file will be included if it exists
	if (file_exists($filename)) {
		$data = @unserialize(file_get_contents($filename));
	}
	// cache file will be created if didn't existed or refreshed all 2 seconds
	if (!$data || filemtime($filename) + 2 < $now) {
		// read data (db query...)
		$data = array(
			'id' => 1111,
			0 => 'long text',
			1 => 'long text',
			2 => 'long text with quotes',
		);
		// write cache file
		// we do not need to lock, as unserialize results false if data set is corrupt
		$h = @fopen($filename, 'w');
		@fwrite($h, serialize($data));
		@fclose($h);
		@umask(0000);
		@chmod($filename, 0644);
	}
	// only for the benchmark to avoid caching
	clearstatcache();
*/
?>

/*
	// version 3
	// run: [b]0.243602633478[/b]
	// run: 0.245651497837 10 secs
	// run: 0.233414025306 30 secs
	// fastest run: 0.114813804626
		$data = array();
	$h = fopen($filename, 'a');
	if (flock($h, LOCK_EX | LOCK_NB)) {
		$data = @unserialize(file_get_contents($filename));
	}
	if (!$data || filemtime($filename) + 2 < $now) {
		// read data (db query...)
		$data = array(
			'id' => 1111,
			0 => 'long text',
			1 => 'long text',
			2 => 'long text with quotes',
 		);
		// write cache file
		ftruncate($h, 0);
		fwrite($h, serialize($data));
		umask(0000);
		chmod($filename, 0644);
	}
	flock($h, LOCK_UN);
	fclose($h);
	// only for the benchmark to avoid caching
	clearstatcache();
*/
/*
	// version 4
	// [b]run: 0.188958084584[/b]
	// run: 0.185067784788
	// fastest run: 0.0628659725189
	// cache file will be created if didn't existed or refreshed all 2 seconds
	// we removed file_exists() as we expect in 99% of all cases that the file is 
	// existing and if not, file_get_contents() does the same for us
	if (!($data = @file_get_contents($filename)) || ($data = @unserialize($data)) === false || filemtime($filename) + 2 < $now) {
		// read data (db query...)
		$data = array(
			'id' => 1111,
			0 => 'long text',
			1 => 'long text',
			2 => 'long text with quotes',
 		);
		// write cache file
		// we do not need to lock, as unserialize results false if data set is corrupt
		$h = @fopen($filename, 'w');
		@fwrite($h, serialize($data));
		@fclose($h);
		@umask(0000);
		@chmod($filename, 0644);
	}
	// only for the benchmark to avoid caching
	clearstatcache();
*/
/*
	// version 5
	// [b]run: 0.0989973068235[/b]
	// run: 0.0999602222446
	// fastest run: 0.0978970527649
	// our script results more than 100 hits per second, so we add a random
	// switch to reduce usage of filemtime()
	// if you run this script on a website, you have to count your daily impressions
	// and decide how much filemtime() requests are needed to find the balance between
	// cache actuality and interval. f.e.: you have a birthday data cache and you want
	// to refresh it every 24 hours. your website results 100.000 impressions per day.
	// i would choose 100 as a good random factor as there are 1.000 impressions left
	// to refresh the cache. one of them should hit between 00:00 and 00:59 to result
	// actual birthday data on the website (with factor 100 apprx. 42 impressions per
	// hour can hit our random factor)
	if (!($data = @file_get_contents($filename)) || ($data = @unserialize($data)) === false || (rand(0, 100) == 100 && filemtime($filename) + 2 < $now)) {
		// read data (db query...)
		$data = array(
			'id' => 1111,
			0 => 'long text',
			1 => 'long text',
			2 => 'long text with quotes',
 		);
		// write cache file
		// we do not need to lock, as unserialize results false if data set is corrupt
		$h = @fopen($filename, 'w');
		@fwrite($h, serialize($data));
		@fclose($h);
		@umask(0000);
		@chmod($filename, 0644);
	}
	if (isset($h)) {
		// only for the benchmark to avoid caching
		clearstatcache();
	}
*/

Mach mit!