There are no real developer programs for PHP as it is simply text based...
If you're using windows try:
Textpad, PHPed and PHPedit
For linux development I'd suggest glimmer or vanta
my requerements for a php development program is basically to be able to do syntax highlighting.
You mind want to try the Zend.com's developer kit... I haven't used it mysqlf (can't afford it 🙂) but i hear it's very good, especially in combination with the debug server.