I've been using PhpStorm for a few years now. After going through several time-wasting periods of trying out every IDE I could get my hands on to see what I liked, I ended up and have stayed with PhpStorm because it is hands down the most feature-full, fast, stable and up-to-date IDE for PHP (and HTML/JS!) development.
It also does not hurt that they're going on a Vagrant rampage and have been showing off my app, https://puphpet.com :)