I'll second Ruby because of Sinatra and add some of my own thoughts. Sinatra is a very gentle introduction to separation of concerns. You can get a Sinatra app running on a shared Dreamhost with the same effort as a PHP site.

PHP was ok for me I spent a ton of time looking up functions in the docs but I could get stuff done. Once I had to edit/work with 3rd party code it was a nightmare.

I've developed in PHP, Ruby, C#, Java, ActionScript, and Python and Ruby's gem system is by far the easiest package management system I've used. Making your own gem is really easy.

Great ideas seem to pop up in Ruby first and then are ported to PHP, so why not use the original (see Rails, Cucumber, Bundler).