[ticket/16955] Add stubs for cache classes and clean up

PHPBB3-16955

tests/cache/cache_memory.php

@@ -23,40 +23,26 @@ class phpbb_cache_memory extends \phpbb\cache\driver\memory
 	}
 
 	/**
-	* Fetch an item from the cache
-	*
-	* @access protected
-	* @param string $var Cache key
-	* @return mixed Cached data
-	*/
-	function _read($var)
+	 * {@inheritDoc}
+	 */
+	protected function _read(string $var)
 	{
 		return $this->data[$var] ?? false;
 	}
 
 	/**
-	* Store data in the cache
-	*
-	* @access protected
-	* @param string $var Cache key
-	* @param mixed $data Data to store
-	* @param int $ttl Time-to-live of cached data
-	* @return bool True if the operation succeeded
+	* {@inheritDoc}
 	*/
-	function _write($var, $data, $ttl = 2592000)
+	protected function _write(string $var, $data, int $ttl = 2592000): bool
 	{
 		$this->data[$var] = $data;
 		return true;
 	}
 
 	/**
-	* Remove an item from the cache
-	*
-	* @access protected
-	* @param string $var Cache key
-	* @return bool True if the operation succeeded
-	*/
-	function _delete($var)
+	 * {@inheritDoc}
+	 */
+	protected function _delete(string $var): bool
 	{
 		unset($this->data[$var]);
 		return true;