Pure dependency-less memcache class implementation for development purposes that saves data to local storage.

Memcache.php

<?php

// Ever needed to test an application that uses Memcache but didn't have it installed locally?
// This class saves its information to a local folder named "data" with the raw data passed to it.
// Each different key saved creates a new file on your system.
// Currently the only methods supported are Memcache::get and Memcache::set.


/**
 * A class that mimicks the Memcache php dependency minimalistically by saving data to local storage.
 *
 * @usage:
 * $memory = new Memcache();
 * $memory->set("hello-world", "my stringifiable data");
 *
 * // On another random request or 300 days later at the artic:
 *
 * $memory = new Memcache();
 * $message = $memory->get("hello-world");
 * assert($message == "my stringifiable data");
 */
class Memcache {
	private function key_to_filename($key) {
		$str = strip_tags($key);
		$str = preg_replace('/[\r\n\t ]+/', ' ', $str);
		$str = preg_replace('/[\"\*\/\:\<\>\?\'\|]+/', ' ', $str);
		$str = strtolower($str);
		$str = html_entity_decode( $str, ENT_QUOTES, "utf-8" );
		$str = htmlentities($str, ENT_QUOTES, "utf-8");
		$str = preg_replace("/(&)([a-z])([a-z]+;)/i", '$2', $str);
		$str = str_replace(' ', '-', $str);
		$str = rawurlencode($str);
		$str = str_replace('%', '-', $str);
		return $str;
	}

	/**
	 * Saves to persistent storage the value of a key
	 *
	 * @param string $key   The key to identify the saved value so that it can be retrieved later.
	 * @param mixed $value  The data as string to be saved to the file or the boolean 'false' to delete the key.
	 */
	public function set($key, $value) {
		if (!is_dir(__DIR__."/data")) {
			mkdir(__DIR__."/data");
		}
		$filename = $this->key_to_filename($key);
		$filepath = __DIR__."/data/".$filename.".txt";
		if ($value === false) {
			unlink($filepath);
			return;
		}
		file_put_contents($filepath, $value);
	}

	/**
	 * Retrieves from the persistent local storage the data previously saved as string.
	 *
	 * @param  string $key The same key used to write data.
	 * @return mixed       The false boolean value if it doesn't exist, a string with its content otherwise.
	 */
	public function get($key) {
		if (!is_dir(__DIR__."/data")) {
			return false;
		}
		$filename = $this->key_to_filename($key);
		$filepath = __DIR__."/data/".$filename.".txt";
		if (!file_exists($filepath)) {
			return false;
		}
		return file_get_contents($filepath);
	}
}