Its just one of several languages, and one that (like most other languages) has some serious flaws. Ive been a php, Java, CSharp/VB developer and I am now looking quite interestedly at Ruby. Ive on Web, Mobile and Desktop apps and I honestly think that only by look around at what others are doing can you really improve.

The number 1 reason I would pick php would be if I were building a content heavy website and needed a CMS. Php has thousands of them out there.

I myself very, very rarely build such things anymore (as there is very little challenge in such a thing). But if I would have to if I had stuck solely to php developer, as those are the only real jobs you can get in my area as a php guy.