What are the contenders?
Netbeans 6.7 with PHP supportAptana 1.5 (standalone or Eclipse plugin)Zend Studio 6.1.2 (not free ;( )
My experiences:
Code completion/parser in Netbeans better than Aptana (Aptana also crashes / gets in a endless loop at points when it cannot parse / code assist a file resulting in java heap exhaustion / cpu up 50%)
Aptana [...]
FB Series: Choosing an PHP IDE