Use what you know best. I don't like the feel of writing Java personally and never had to take any Java programming classes to force me into it. PHP on the other hand is very easy and natural to write, but the code can end up damn ugly. I also haven't looked into it too much, but I think Java beats out PHP for performance speed. Both have pros and cons.

If it were me I'd suggest Python. I need to look into web.py some more, but I currently use Django for most web things. It's easy to write the code and doesn't end up looking like ass so it's easier to maintain.