public function remember_me($user_id = null)
	{
		// if no user-id is given, get the current user's id
		if ($user_id === null and isset($this->user['id']))
		{
			$user_id = $this->user['id'];
		}

		// if we have a session and an id, set it
		if (static::$remember_me and $user_id)
		{
			static::$remember_me->set('user_id', $user_id);
			return true;
		}

		// remember-me not enabled, or no user id available
		return false;
	}