I like PHP since it is so easy to deploy and it can be used for anything from a simple two page website to a full-blown web application. Being written in PHP also means that you are not limited in hosting.
If you're a startup creating a single web app, then fine, use Python with mod_wsgi or Rails and five mongrel servers. But if you're creating basic CRUD websites, especially more than one, then there is nothing wrong with PHP. I can fit dozens of low-traffic websites on a $20/mo 256MB RAM server using Apache and mod_php; try doing that with Rails.
As I said, if I was going to focus on a single web app with its own dedicated server, then I would definitely look at Python and mod_wsgi, but since I create a lot of 'smaller' websites (nothing too complex), it is much less of a hassle using PHP since I can fit all of them nicely on a single, cheap server.