For your case, don't use Python, nor PHP. Both are pretty much just like Perl and Java with only minor syntax changes.
If you want to expand your understanding of computing in general, while also learning a new language, and while doing a webapp, if I were you I'd learn Common Lisp and try out Hunchentoot. There's even some screencasts for that setup floating around.
Going with Python or PHP after Perl and Java is not going to be terribly enlightening for you.
I've also been learning Lisp (sbcl) over the last six months and have tried out Hunchentoot with elephant, cl-who, and parenscript.
I'd say one of the things keeping me from going with Lisp is the potential pool of developers to pick from when expanding the operation. I think I would have a better chance at enlisting others with PHP or Python than with Common Lisp. Is this line of thinking wrong?
For your case, don't use Python, nor PHP. Both are pretty much just like Perl and Java with only minor syntax changes.
If you want to expand your understanding of computing in general, while also learning a new language, and while doing a webapp, if I were you I'd learn Common Lisp and try out Hunchentoot. There's even some screencasts for that setup floating around.
Going with Python or PHP after Perl and Java is not going to be terribly enlightening for you.