Oh it seemed as if you were asking about actually launching an ftp client application. It would help to explain yourself a bit more because not everyone--including myself--knows what slimftpd is, or how it applies to PHP code.
A Google search later...
SlimFTPd site wrote:SlimFTPd is a fully standards-compliant FTP server
It would have helped to include that somewhere in your two posts here.
I recommend using [php_man]exec()[/php_man]. It will most likely be of great service to you if you create a batch (.bat) file, or if that application has executables to stop/start/restart (like Apache can). That way you can simply exec() the right executable to do the task you want.