Difference between SharePoint and php

Hi there, was wondering if you could possibly give me a quick run down on the differences between SharePoint and using php. I am very knowledgeable in this area, but I have seen some of the web sites that use php and they are very user friendly. I am in the process of trying to get some buy in for user forums for the Ministry of Forests but need to know what this would entail. Degree of difficulty, Cost, Security, and support are some of the big issues. The reason I bring up SharePoint is I see it is in test mode in one of our applications. Thank you. Christine