How to execute System Calls in a secure way?

[Ste <stefanmeier () freesurf ch>]

Can anyone help out with the following problem:

Situation Description:

A PHP Webgui of an internal Management System needs to validate 
Input by an external Program (which need's root privileges). How can 
this be done in a secure matter? Would it be better to run the Program 
as suid, RBAC or are there other/better solutions?

Thanks for answers in advance