Help for ISPs rolling out PHP

I'm working with a medium sized ISP to start rolling out PHP and MySQL services to customers. I've been looking around for best practices or help with such a roll out but not found anything. I'm confident I can roll out the services but with so many other ISPs currently running PHP it seems like I could save my self a lot of mistakes and grief if I could learn from admins that have already done it. Is anyone aware of a resource specifically about rolling out PHP to a large number of users in an ISP setting? Specifically dealing with security issues like a user doing an unlink(../otheruser/index.html); ? Any pointers and experience are appreciated. Thank You. technikolor