I like PHPdesigner 2008... or dreamweaver... If you're looking for something free then go for notepad++ or something like that
I really like Aptana which is free and NetBeans. Eclipse PDE is quite nice too. What's cool is to have an upload on save feature.
I use vim for small changes and eclipse for dealing with bigger projects. There is no "best" editor, it's mainly just a preference...
PHPDESIGNER hands down has live php error detector and everything you need in a ide.... and dream weaver for the design aspect.