public static function get_fullname_field($firstnamefirst = false) {
        global $DB;
        if ($firstnamefirst) {
            return $DB->sql_fullname(self::resolve_field('firstname', 'user'), self::resolve_field('lastname', 'user'));
        }
        return $DB->sql_fullname(self::resolve_field('lastname', 'user'), self::resolve_field('firstname', 'user'));
    }