I had some issues installing Eclipse PDT on Ubuntu Maverick 10.10. Finally, the solution could be found here: https://help.ubuntu.com/community/EclipsePDT
From Synaptic Package Manager and Update Site
NOTE: On Ubuntu 10.10 this method will install Eclipse 3.5 (Galileo) and PDT 2.1.
* Open Synaptic Package Manager (System->Administration->Synaptic Package Manager)
* Find the package "eclipse" and mark it for installation
* Click Apply
Install PHP Development Tools (PDT)
* Open Eclipse and specify your workspace (Applications->Programming->Eclipse)
* Help->Install New Software
* Select the Galileo Update site
* Select the PHP Development Tools (PDT) Feature
BUT! ... you have to know that you need to run Eclipse as root for the second part of the installation. If you don't do it, you will not get an error. You will just not be able to access PDT features :-( ...