bash - what is the best way to run shell script (with root privilege) via php?

I've made a simple bash script for server admininstration and I cannot figure how can I run it in safely inside a php page: I'd like to create a php admininstration page but I obviously don't want to hard-code root password anyware. Let's make an example (this is a foo script, of course)

#!/bin/bash
touch /$1
Copy code

this simple/stupid script will not work if the user who run it as no writing permission on /.
Actually the script add apache virtualhosts, ftp users and so on... any ideas?
thanks