The best professional editor is currently Zend Studio from Zend Technologies. Similar to what Maguma had in mind, the Zend Studio can integrate wit a server side development and deployment platform, the Zend Server.
NuSphere also has a more basic PHP editor called PhpEd. Balanced combination of code editor, debugger, database connectivity client and fast and secure deployment abilities make PhpED a complete solution for most developer needs.
An interesting twist on PHP editors is Delphi for PHP, a integrated, rapid visual development approach and component framework for PHP.