Sure, in a nutshell:
Solution1) - (real time)
1) install sudo
2) run apache on a secure port as a different user (wwwadmin)
3)define a sudo library for for wwwadmin
4)exec $sudo $command
Adduser functions are available only to root - and running apache as root is considered a security hole by people with common sense.
Solution2) - (scheduled task)
Write request to cron and have it executed as root on a periodic basis.
Hope this helps a bit.
-m.
