I'd second the Python recommendation. Switching from custom PHP to Python (specifically Django) saved me a ton of development headaches.
Though, Django is pretty slower than any PHP framework(from the frameworks I've worked with)
Django was actually my first use of Python - so you can imagine how pleased I was to replace a custom PHP app with something I just learned - and in record time. (if you're interested, the web app was: http://www.snapact.com/)
I have noticed no issues with performance as compared to PHP.
http://www.alrond.com/en/2007/jan/25/performance-test-of-6-l...