They all understand PHP code and will use color coding and include a number of tools to assist developers.
Blaine
It's also freeware.
You can find it at http://www.crimsoneditor.com/
Granted, older versions of Dreamweaver may not work, but MX certainly does and I'd recommend it. It's also great for theme files (just add the .thtml extension to the list in preferences).
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L. Whitworth
www.finiserv.com