I was recently asked to do a simple order page for a company where I know a guy. It would be a simple page with a few web forms, emailing the order to them. That's all they needed. I chose PHP because:

1. Even though I haven't used it in a while it is super simple to get in to. 2. They did not pay me to learn new stuff. They did not need a fancy web framework. They don't care about code elegance. 3. They already had a web site hosted on server with PHP. 4. Development environment is easy to setup locally (just download a portable PHP dev env and run). Everything is built in. 5. Passing it on to them, it's just a few text files to upload that they can easily modify as needed. Nothing to compile.

In short, it's just the simplest way to do it sometimes (KISS). And not all projects are big enough to justify more complex solutions.