There is no question that PHP is extremely popular; in fact, it's currently the most popular open source programming language. There are always PHP developers available and there are always PHP jobs around. And this demand generally translates into a large pool of developers that can be tapped into when you want to expand your team.
Python has never been that popular. However, counter intuitively, its lack of popularity compared to PHP can sometimes be a strength. Python developers may be somewhat rarer, but I've found they are often of much higher quality. While I'm sure there are some bad Python developers out there in the market, I have never had a job interview with one of them. I would love to be able to say the same thing about PHP developers.
On a purely personal level, I'm left with the overriding feeling that PHP is like Play-Doh. You can make anything you want out of it, but at the end of the day it's still made out of Play-Doh.