The Eclipse PDT (PHP Development Tools) project is a joint effort between Zend and IBM to produce a standard set of plugins for PHP developers to work on Eclipse. The main features are:
The main project website is here:
I would recommend using the "complete" package from the Zend site, as it contains the Zend Debugger configured as part of the Eclipse 3.3 build:
"http://www.zend.com/pdt" (now dead, see note below)
I have been playing around with this on my laptop and it is very sweet, the code assist works really well. If you add Subclipse into the equation you will have everything you need for a very powerful IDE for building PHP applications:
"http://subclipse.tigris.org/" (now dead, see note below)
Updated 2021 : note that the above post was originally published in 2007, but is left here for archival purposes. While it seems that the main Eclipse PHP Development Tools project is still going strong, the other links above and now dead so I had to unlink them.