I don't know what instructions support gave you, but the ones located in the wiki are what you should be following to get PHP working properly.
Assuming you want PHP5, the wiki link for that is here:
I don't know how else to help you other than to point you at that wiki entry, and suggest you follow it exactly as it says. If something goes wrong, then you've probably missed a step. Just go back and double-check you did everything exactly as it says