Add Memcached caching driver

qa-include/Q2A/Storage/MemcachedDriver.php

+<?php
+/*
+	Question2Answer by Gideon Greenspan and contributors
+	http://www.question2answer.org/
+
+	File: qa-include/Q2A/Storage/MemcachedDriver.php
+	Description: Memcached-based driver for caching system.
+
+
+	This program is free software; you can redistribute it and/or
+	modify it under the terms of the GNU General Public License
+	as published by the Free Software Foundation; either version 2
+	of the License, or (at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	More about this license: http://www.question2answer.org/license.php
+*/
+
+/**
+ * Caches data (typically from database queries) in memory using Memcached.
+ */
+class Q2A_Storage_MemcachedDriver implements Q2A_Storage_CacheDriver
+{
+	private $memcached;
+	private $enabled = false;
+	private $error;
+	private $flushed = false;
+
+	const HOST = '127.0.0.1';
+	const PORT = 11211;
+
+	/**
+	 * Creates a new Memcached instance and checks we can cache items.
+	 * @param array $config Configuration data, including cache storage directory.
+	 *
+	 * @return void
+	 */
+	public function __construct($config)
+	{
+		if (!$config['enabled']) {
+			return;
+		}
+
+		if (extension_loaded('memcached')) {
+			$this->memcached = new Memcached;
+			$this->memcached->addServer(self::HOST, self::PORT);
+			if ($this->memcached->set('q2a.test', 'TEST')) {
+				$this->enabled = true;
+			} else {
+				$this->setMemcachedError();
+			}
+		} else {
+			$this->error = 'The Memcached PHP extension is not installed';
+		}
+	}
+
+	/**
+	 * Get the cached data for the supplied key. Data can be any format but is usually an array.
+	 * @param string $key The unique cache identifier.
+	 *
+	 * @return mixed The cached data, or null otherwise.
+	 */
+	public function get($key)
+	{
+		if (!$this->enabled) {
+			return null;
+		}
+
+		$result = $this->memcached->get($key);
+
+		if ($result === false) {
+			$this->setMemcachedError();
+			return null;
+		}
+
+		return $result;
+	}
+
+	/**
+	 * Store something in the cache along with the key and expiry time. Data gets 'serialized' to a string before storing.
+	 * @param string $key The unique cache identifier.
+	 * @param mixed $data The data to cache (in core Q2A this is usually an array).
+	 * @param int $ttl Number of minutes for which to cache the data.
+	 *
+	 * @return bool Whether the file was successfully cached.
+	 */
+	public function set($key, $data, $ttl)
+	{
+		if (!$this->enabled) {
+			return false;
+		}
+
+		$ttl = (int) $ttl;
+		$expiry = time() + ($ttl * 60);
+		$success = $this->memcached->set($key, $data, $expiry);
+
+		if (!$success) {
+			$this->setMemcachedError();
+		}
+
+		return $success;
+	}
+
+	/**
+	 * Delete an item from the cache.
+	 * @param string $key The unique cache identifier.
+	 *
+	 * @return bool Whether the operation succeeded.
+	 */
+	public function delete($key)
+	{
+		if (!$this->enabled) {
+			return false;
+		}
+
+		$success = $this->memcached->delete($key);
+
+		if (!$success) {
+			$this->setMemcachedError();
+		}
+
+		return $success;
+	}
+
+	/**
+	 * Delete multiple items from the cache.
+	 * @param int $limit Maximum number of items to process. 0 = unlimited
+	 * @param int $start Offset from which to start (used for 'batching' deletes).
+	 * @param bool $expiredOnly This parameter is ignored because Memcached automatically clears expired items.
+	 *
+	 * @return int Number of files deleted. For Memcached we return 0
+	 */
+	public function clear($limit = 0, $start = 0, $expiredOnly = false)
+	{
+		if ($this->enabled && !$expiredOnly && !$this->flushed) {
+			$success = $this->memcached->flush();
+			// avoid multiple calls to flush()
+			$this->flushed = true;
+
+			if (!$success) {
+				$this->setMemcachedError();
+			}
+		}
+
+		return 0;
+	}
+
+	/**
+	 * Whether caching is available.
+	 *
+	 * @return bool
+	 */
+	public function isEnabled()
+	{
+		return $this->enabled;
+	}
+
+	/**
+	 * Get the last error.
+	 *
+	 * @return string
+	 */
+	public function getError()
+	{
+		return $this->error;
+	}
+
+	/**
+	 * Get current statistics for the cache.
+	 *
+	 * @return array Array of stats: 'files' => number of files, 'size' => total file size in bytes.
+	 */
+	public function getStats()
+	{
+		$stats = $this->memcached->getStats();
+		$key = self::HOST . ':' . self::PORT;
+
+		$totalFiles = isset($stats[$key]['curr_items']) ? $stats[$key]['curr_items'] : 0;
+		$totalBytes = isset($stats[$key]['bytes']) ? $stats[$key]['bytes'] : 0;
+
+		return array(
+			'files' => $totalFiles,
+			'size' => $totalBytes,
+		);
+	}
+
+	/**
+	 * Set current error to Memcached result message
+	 *
+	 * @return void
+	 */
+	private function setMemcachedError()
+	{
+		$this->error = 'Memcached error: ' . $this->memcached->getResultMessage();
+	}
+}