I work as a full time web developer and am required to use PHP for everything server side. It's one of the worst languages I have ever used but I live in a LAMP world and everyone requires me to use it.

I have used Clojure and RoR in the past and really like them but unfortunately I can't use them in reality. I wrote about it in this post on my blog.

http://www.codeinnovator.com/uncategorized/lisp-vs-php/

You can certainly develop professionally with it. It's just not a whole lot of fun.