protected function addMessage($message) {
		$hash = crc32(json_encode(func_get_args()));
		
		if (isset($this->_messages[$hash])) {
			return;
		}
		
		if (func_num_args() > 1) {
			$this->_messages[$hash] = call_user_func_array('sprintf', func_get_args());
		} else {
			$this->_messages[$hash] = (string) $message;
		}
	}