The Zend IDE project has met with some different kinds of receptions, but overall, the preview release seems to show promise. The PHPEclipse project has been around a bit longer, but hasn't really caught on. To compare the two, Florian Anderiasch thought he'd take his own look and see how they compared with each other and how they matched up with his expectations.
I've felt the need to both test both the Zend IDE and phpeclipse and so I made a little thing for practice and to fiddle around a bit.
Just a very quick and rudimentary roundup, but imho especially an IDE shouldn't get in the programmer's way and do just what it should be - aid development.
He mentions being surprised and impressed by PHPEclipse, while left a bit cold by Zend's offering ("I wasn't able to work with a file of just 500 lines because it felt more frozen than sloppy"). His personal choice for larger projects? PHPEclipse.