As all aptana fans know, Aptana PHP plugin was discontinued in Aptana 2.x, in favor of PDT.
But PDT is a joke, not suitable for professional PHP development, major features are missing.
So if you want to continue using Aptana PHP, that’s what need to be done:

1. Aptana -> Install New Software
2. Add http://update.aptana.com/install/php
3. Then select Aptana PHP and install it.

In case you don’t have yet a SVN plugin, go to

1. Install Aptana Features
2. Others -> Subclipse
3. Follow the instructions