I started with PHP and I wouldn't recommend it. It teaches you horrible habits and its type system is equally confusing if you get started or if you come from another language. Plus, you have that heavily polluted global namespace, a half-assed class system (objects are special, classes are special, primitives are special -- in Python the experience is closer to "OMG I've been using objects all along!" (like in those movies where the protagonist suddenly realises the shoes weren't magical, "the magic was in [him]") whereas in PHP you actually need to understand a completely different approach to what you're used to.
And don't get me started on naming conventions. Sure, you can adapt to PHP's inconsistencies, but ideally the first language you learn should be reliable and consistent.
BESIDES: if you learn a web language, you have to learn HTML first. And if you want to learn HTML these days, you also have to learn CSS and then JavaScript isn't far off either. In short: you'll have to learn a whole lot of stuff just to get anywhere. If you start coding in a shell and eventually start on GUI code, you only have to worry about what it all looks like on YOUR machine (and if you want to share your code, you can simply (have your daddy) make sure the other person has all the necessary modules in place).