Short answer:
If you love coding, learn Python. If making web apps is just a means to an end for you, learn PHP (and a framework like Code Igniter).
Long answer: If you want to code web apps primarily for the forseeable future, go with PHP and a great backend framework like Code Igniter.
If you want to eventually code larger scale backend pieces, and grow into other areas of development, go with Python.
I love Python, but have a renewed loss of skepticism for PHP given how well CodeIgniter has performed for some of our major web apps. I personally feel Python doesn't feel as inherently interconnected with web concepts as PHP, so there are more complications/hurdles to get past in order to build a 100% functional/pretty web app. But you'll be much better off long-term for learning Python if you're going into sysadmin/backend/app development.
I love coding, so I learned both. Good luck!