A (very) simple file based cache script. The class works great for my older pages on www.finalwebsites.com (all pages that are not served by WordPress)

FileCache.class.php

<?php

class FileCache {

	protected $cacheValidTime;
	public $cacheIsValid = false;
	protected $cacheFile;

	function __construct($file, $valid = 86400) {
		$this->setCacheFile($file);
		$this->setCacheTime($valid);
		if (!DEBUGTEST) {
			if ($this->checkValidCache()) {
				$this->cacheIsValid = true;
			}
		}
	}


	protected function setCacheFile($file) {
		$this->cacheFile = CACHEDIR.$file.'.cache';
		if (dirname($this->cacheFile) != CACHEDIR && !file_exists(dirname($this->cacheFile))) {
			mkdir(dirname($this->cacheFile), 0755, true);
		}
	}

	protected function setCacheTime($time) {
		$this->cacheValidTime = $time;
	}

	protected function checkValidCache() {
		$valid = false;
		if (file_exists($this->cacheFile) && filesize($this->cacheFile) > 0) {
			$timedif = (time() - filemtime($this->cacheFile));
			if ($timedif < $this->cacheValidTime) {
				$valid = true;
			}
		}
		return $valid;
	}

	public function readCache() {
		$handle = fopen($this->cacheFile, "r");
		$contents = fread($handle, filesize($this->cacheFile));
		fclose($handle);
		return $contents;
	}

	public function writeCache($data) {
		if ($data == '') return;
		$fp = fopen($this->cacheFile, 'w');
		if (flock($fp, LOCK_EX)) {
			if (fwrite($fp, $data) === FALSE) {
				$this->mailError('Can\'t write the cache file: '.$this->cacheFile);
			}
			flock($fp, LOCK_UN);
		} else {
			$this->mailError('Can\'t lock the cache file: '.$this->cacheFile);
		}
		fclose($fp);
	}

	protected function mailError($msg) {
		//mail('your@email.com', 'Error in '.__CLASS__.' at '.date('Y-m-d'), $msg);
	}
}
/* Example */
/*
$cache = new FileCache('yourPHPfile.php', 86400); // cache is valid for one day
if ($cache->cacheIsValid) {
	echo $cache->readCache();
} else {
	// Place here the PHP and HTML code
	$data = 'abc';
	$cache->writeCache($data);
	echo $data;
}
*/