Where do you find it? Eclipse that I am aware of is Java not PHP.
Yes, it is (built on) Java, but there a lot of versions:
Eclipse IDE for Java EE Developers
Eclipse IDE for Java Developers
Eclipse for PHP Developers
Eclipse IDE for C/C++ Developers
Eclipse for RCP/Plug-in Developers
Eclipse SOA Platform for Java and SOA Developers
Eclipse IDE for Java and Report Developers
Eclipse Modeling Tools
Pulsar for Mobile Java Developers
Eclipse Classic 3.5.1
...and I'm interested in the Eclipse for PHP developers. Maybe there >might< be some differences on how to run it between the different versions.