i was used to use notepad and "Free Script Editor" by www.freescripteditor . org but seeing so many others i will try them.
Zend studio 5.5 here, the link with zend platform is rather handy and has good support for live editing. Others: notepad++ - wasn't supported in linux at the time + no ftp/sftp support that saw bluefish - pretty nice linux one, unsure if still around vim - mostly in anger / for speed
I have always used DW and/or Textpad. I recently tried codelobster, and low and behold, I STILL use DW and Textpad!
Dreamweaver is by far the best, it comes with it's own PHP reference (expensive). PHPEdit is free and good!