I've always used MAMP. It's very easy to set up and use, and there's absolutely no reason not to trust it. I've also tried enabling PHP on the ~/Sites folder (Macs come with all that, but you have to tweak it) but it was a hassle to set up and I ran into various problems when using.

In short, I recommend MAMP.

You could also try the Eclipse PDT and ZendServer Community Edition if you are needing it more for development with debugging capabilities.

www.zend.com

Im new to macs but i have a great time usin www.mamp.info and it seems to work perfectly