From what I've heard and seen, PHP is pretty messy? I'm sure I'll get burned for saying that considering it is an open/free language/tool.
Personally (and my life is writing business applications) I'd use something that is going to be easy to design (structurally, not UI wise) and even easier to maintain). Hence my choice of Java

In addition, I've almost got a 'thing' against using browsers to deliver business applications. I just don't think it is right! - a browser is to deliver web pages, not applications. You end up with a slow interface with a gui that isn't rich, and will ultimately be hard to maintain. Anyway, I can go on about this topic!!