private function _key($identifier) {
    	extract($identifier);
    	$arg_string = "";
    	return md5(serialize($class . $method . implode('~', $args)));
    }
private function _key($identifier) {
    	extract($identifier);
    	$arg_string = "";
    	return md5(serialize($class . $method . implode('~', $args)));
    }
private function _key ( $ identifier ) { extract ( $ identifier ) ; $ arg_string = "" ; return md5 ( serialize ( $ class . $ method . implode ( '~' , $ args ) ) ) ; }
Creates a key for cached class methods
@param  array $identifier  class|method|args
@return string
Creates a key for cached class methods