Definitelly PHP, because I have a friend who is a wizard in PHP, so why not exploit that when you can. It's always nice to have a friend, haha! I'm so bad...
I choose PHP because it is widely supported and the open source community exploits it so much. It's easier to learn also, in my opinion.
Yes agree on that. I too usually tend to go with technologies and languages that are widely supported and have the community of people that are willing to help you. Learning is much easier that way.
The choice of which development language to use commonly comes down to two popular choices asp or php. But why one might choose one over the other? IMO, mostly people choose php due the low cost of development, availability of tools, and comfort level with the open source. Any all it depends on users choice. You should consider following chart to analyze which one meets your demands.