I tried that friend site.. I see that I get a Database error.. Looks pretty unsafe to me.
Database Exception
SQLSTATE[42S22]: Column not found: 1054 Unknown column 'CASE WHEN bot THEN 9 WHEN gold THEN 0 ELSE 1 END' in 'order clause'
The SQL being executed was: SELECT `user`.* FROM `user` `user` LEFT JOIN `user_travels` `travels` ON `user`.`id` = `travels`.`user_id` LEFT JOIN `profile` `profile` ON `user`.`id` = `profile`.`user_id` INNER JOIN `active_users` `active` ON (`user`.`id` = `active`.`user_id`) AND (`expires_at` > 1530522537) WHERE `visibility`=1 GROUP BY `user`.`id` ORDER BY `CASE WHEN bot THEN 9 WHEN gold THEN 0 ELSE 1 END`, `last_online` DESC, `created_at` DESC LIMIT 36