FileSystem Storage Concept

fsstorage.php

<?php

class FSStorage {

	protected $dir;

	public function __construct($dir) {
		$this->dir = $dir;
	}

	public function set($key, $data) {
		$path = $this->getPath($key);
		$dir = dirname($path);
		if (!is_dir($dir)) mkdir($dir, 0700, true);
		file_put_contents($path, $data, LOCK_EX);
		clearstatcache();
	}

	public function get($key, $ttl = 0) {
		$path = $this->getPath($key);
		if (!is_file($path)) return null;
		$mtime = filemtime($path);
		if ($ttl && ($mtime + $ttl) < time()) return null;
		$f = fopen($path, 'rb');
		flock($f, LOCK_SH);
		$data = fread($f, filesize($path));
		flock($f, LOCK_UN);
		return $data;
	}

	protected function getPath($key) {
		$hash = md5($key);
		$parts = array_slice(str_split($hash, 2), 0, 4);
		$path = rtrim($this->dir, '/') . '/'
		$path .= implode('/', $parts);
		$path .= "/$hash";
		return $path;
	}

}