Add interface for cache drivers

qa-include/Q2A/Storage/CacheDriver.php

+<?php
+/*
+	Question2Answer by Gideon Greenspan and contributors
+	http://www.question2answer.org/
+
+	File: qa-include/Q2A/Storage/FileCache.php
+	Description: Interface for drivers of 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
+*/
+
+/**
+ * Interface for caching drivers.
+ */
+interface Q2A_Storage_CacheDriver
+{
+	/**
+	 * 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);
+
+	/**
+	 * 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);
+
+	/**
+	 * Delete an item from the cache.
+	 * @param string $key The unique cache identifier.
+	 *
+	 * @return bool Whether the operation succeeded.
+	 */
+	public function delete($key);
+
+	/**
+	 * 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 $expiredOnly Delete cache only if it has expired.
+	 *
+	 * @return int Number of files deleted.
+	 */
+	public function clear($limit = 0, $start = 0, $expiredOnly = false);
+
+	/**
+	 * Whether caching is available.
+	 *
+	 * @return bool
+	 */
+	public function isEnabled();
+
+	/**
+	 * Get the last error.
+	 *
+	 * @return string
+	 */
+	public function getError();
+
+	/**
+	 * Get current statistics for the cache.
+	 *
+	 * @return array Array of stats: 'files' => number of files, 'size' => total file size in bytes.
+	 */
+	public function getStats();
+}

qa-include/Q2A/Storage/FileCacheDriver.php

@@ -23,7 +23,7 @@
 /**
  * Caches data (typically from database queries) to the filesystem.
  */
-class Q2A_Storage_FileCacheDriver
+class Q2A_Storage_FileCacheDriver implements Q2A_Storage_CacheDriver
 {
 	private $enabled = false;
 	private $error;
@@ -58,6 +58,7 @@ class Q2A_Storage_FileCacheDriver
 	/**
 	 * Get the cached data for the supplied key.
 	 * @param string $key The unique cache identifier.
+	 *
 	 * @return string The cached data, or null otherwise.
 	 */
 	public function get($key)
@@ -95,6 +96,7 @@ class Q2A_Storage_FileCacheDriver
 	 * @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)
@@ -120,6 +122,7 @@ class Q2A_Storage_FileCacheDriver
 	/**
 	 * Delete an item from the cache.
 	 * @param string $key The unique cache identifier.
+	 *
 	 * @return bool Whether the operation succeeded.
 	 */
 	public function delete($key)
@@ -139,6 +142,7 @@ class Q2A_Storage_FileCacheDriver
 	 * @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 $expiredOnly Delete cache only if it has expired.
+	 *
 	 * @return int Number of files deleted.
 	 */
 	public function clear($limit = 0, $start = 0, $expiredOnly = false)
@@ -186,6 +190,7 @@ class Q2A_Storage_FileCacheDriver
 
 	/**
 	 * Whether caching is available.
+	 *
 	 * @return bool
 	 */
 	public function isEnabled()
@@ -195,6 +200,7 @@ class Q2A_Storage_FileCacheDriver
 
 	/**
 	 * Get the last error.
+	 *
 	 * @return string
 	 */
 	public function getError()
@@ -204,6 +210,7 @@ class Q2A_Storage_FileCacheDriver
 
 	/**
 	 * Get current statistics for the cache.
+	 *
 	 * @return array Array of stats: 'files' => number of files, 'size' => total file size in bytes.
 	 */
 	public function getStats()
@@ -233,7 +240,8 @@ class Q2A_Storage_FileCacheDriver
 
 	/**
 	 * Delete a specific file
-	 * @param  string $file Filename to delete
+	 * @param string $file Filename to delete.
+	 *
 	 * @return bool Whether the file was deleted successfully.
 	 */
 	private function deleteFile($file)
@@ -248,6 +256,7 @@ class Q2A_Storage_FileCacheDriver
 	/**
 	 * Generates filename for cache key, of the form `1/23/123abc`
 	 * @param string $key The unique cache key.
+	 *
 	 * @return string
 	 */
 	private function getFilename($key)