On the W3Avenue site today there's a list of tools posted that could come in quite handy in your PHP development:

Whether you are a PHP novice or an experienced developer; tools that you use have direct impact on your productivity. W3Avenue has compiled a list of really useful extensions & tools for PHP developers that will help you speed up development and significantly improve overall quality of your code.

They've broken them out into a few different categories - accelerators, build systems, tools applying to code enhancement and correctness, database connectivity, debugging, development/IDEs, security, setup and testing. They also throw in links to a few cheat sheets you can use for quick reference.