http://www.maguma.com/en/lightdownload.html
After Dreamweaver MX randomly broke I needed a new PHP IDE, this is the best freeware one I've found. It has some quirks (some annoying autoindentation that can't be turned off) but the best one I've used.
Check out the sidebar. Makes browsing functions.php really easy

It also has something I love, the 80 char line, so you make sure that your lines of code are easy to read. No other free IDE and not even DWMX had it