Under Windows check out HomeSite, pricy ($100) but worth it (project mgt, developer mapping, snippet library, etc).
There is also TextPad, or UltraEdit, Zend's own IDE, and, of course, gvim.
Or under KDE check out Quanta Plus, vim, gvim...
http://www.macromedia.com/
http://www.wilk4.com/asp4hs/php4hs.htm
http://quanta.sourceforge.net/