It’s very simple right now to get the milestone builds of the PHP Developer Tools (PDT) 3 up and running in Eclipse IDE Indigo release (and a significant improvement on the current Helios SR2 release).
Once installed, launch Eclipse and navigate to Help->Install new Software.
Add the Indigo update site http://download.eclipse.org/releases/indigo . This will take sometime to add, let it go for 5 or so minutes.
Once the Indigo Update Site is added, add the PDT 3.0 Update Site: http://download.eclipse.org/tools/pdt/updates/3.0/milestones/
Now, to install simply select PDT Development Tools All in One SDK (leave the others unselected) and click next. The installation process shouldn’t take more than a few minutes.
(Article copied almost verbatim from Aaron Bonner)