public static function get_popup_notifications_parameters() {
        return new external_function_parameters(
            array(
                'useridto' => new external_value(PARAM_INT, 'the user id who received the message, 0 for current user'),
                'newestfirst' => new external_value(
                    PARAM_BOOL, 'true for ordering by newest first, false for oldest first',
                    VALUE_DEFAULT, true),
                'limit' => new external_value(PARAM_INT, 'the number of results to return', VALUE_DEFAULT, 0),
                'offset' => new external_value(PARAM_INT, 'offset the result set by a given amount', VALUE_DEFAULT, 0)
            )
        );
    }