Uninstalling PHP?

Three weeks ago I was working through the Lynda.com "PHP with MySQL Training" because I wanted to begin using PHP (surprise, surprise). Anyway, on this video course the teacher explains that because installing PHP and MySQL is so well understood on a Mac that we may as well just follow his steps and do it manually. Well, he is installing a different version of PHP and MySQL to the ones that I was able to download and while what he was saying way somewhat similar I am guessing that there is a difference somewhere, and (well) it's not working. I AM A COMPLETE NOVICE WITH LINUX/FREEBSD. It had not been my intention to learn the intricacies of Linux. However, I am now neck deep in a mire of confusion that even MAMP can't seem to sort out for me. It is purely a guess that I need to start again from a complete clean setup (reformatting my hard disk and reinstall OS X again) but that is pretty much out of the question. I guess my question is: "How can I completely uninstall PHP so that I can start again?" Thanks.