Php in itself is difficult for IDEs because of the dynamic nature of the language.
My current development environment is mostly netbeans against a local svn copy of the codebase setup in a local development webserver. The code is full text indexed by vistas search engine for almost instant searches.
I do a lot of development directly against the main development server using a combination of tools. Putty to interact with the server and deploy by updating an svn checkout on the development server. Tortoise SVN locally to have a fairly rich SVN experience. Netbeans obviously have SVN integration. Most of the changes on the remote server is commited using the putty session. WinSCP to interact with the development server with norton commander like interface as well as the good putty integration.
Finally my text editor for remote editing is notepad++ out of habit and because of some nice features and good price.
What I'm really missing is good php editing. Because of the way typo3 works almost all objects are instanciated through make instance abstraction that either returns the base class or the customized class if the framework has been extended. I'm not looking for a magic editing package and would like to find an editor which can use annotations to specify the type of commonly used variables.