Well,
There are several choices when it comes to editors in linux.
1) Emacs/XEmacs http://www.xemacs.com - This is a good all around program that, with the right package, can do syntax highlighting. I use to use this about 8 months ago, but found that it often produced errors.
2) KPHPDev http://kphpdev.sourceforge.net - This editor looked promising for about 10 minutes until I hit S to save the file. It took the first 10 lines and repeated them through my file. This was a hard bug to track down. I was editing my file, tried to save it, tested it and I kept getting errors. Well in KPHPDev, my code looked correct, so I exited out and used VI to look at the source, thats when I found the bug. I highly recommend staying away from this editor for awhile.
3) NEdit http://www.nedit.org - This is the editor I use ( for php, java, and perl). It has syntax highlighting for about any type of language you can think of. It is also nice because there is a GUI for editing the syntax patterns. This editor also allows you to create macros for faster programming. PHP highlighting doesnt come default, but there is a contributed source file on NEdits website. Get the php/html source, it is better than the standard php. This program also comes with its bugs. For one, it will not allow you to edit more than one file at a time if you compile the source on linux, get the binary. After you open up about 20 files, the shortcut keys start messing up, this is fixed by exiting the program and restarting it. By far, I recommend this editor.
4) Code Commander - I didnt use this editor much, but did find out that it has crappy syntax highlighting. If you put an apostrophy in a comment, the entire syntax color is through off. I stopped using it the day I started.
5) Code Warrior http://www.codewarrior.com - I never tried it, but will soon. This is the only commercial application I can think of.
