In the early days of the project, a Tiki Backup (tiki-backup.php) feature was added.
It worked but this is inherently unsafe because it's like performing surgery on yourself. It was progressively removed from the menus and then from the application. In Tiki 4.0, there are no traces left.
Use phpmyadmin or mysqldump instead as described at doc:Backup.
Or even better, use doc:TRIM, dev:TRIM (Tiki Remote Instance Manager), a combination of shell and PHP scripts to install, update, backup, restore and monitor (check security of) a large number of Tiki installations (instances).