Autocompletion in Modules

Hello together,

at first I have to apologize for my english, but I´ll try my best. I`m new to IntelliJ Ultimate and maybe have some "beginner problems":

Afer installing IntelliJ I created a project (as a workspace, like in eclipse) and then installed plugins for PHP Support and configured some editor settings and svn settings.

After that, I checkout several projects from our svn. For your understanding: we have one "core" project and for every our customer a new project, with a customer folder, which overwrites the core files (at runtime). The corefiles are included over svn externals, so when you check out a project, you have all files in your folder.
Those svn projects I added to my workspace as modules. (Read a lot of comments, and thought that this is the best solution. I didn´t want to open every customer project in a single window.)
Now my "workspace" project consists of 20 module. The "core" module, with all files and for each customer one own module, with all files(svn externals) and the customerfolder, with the overwrites.

My problem now is, that if I´m developing in one project (for example a customer project), the autocompletion suggests the methods and parameters from other modules and often doesn´t realise, that it has the neccessary files in it self.
Also, if I want to navigate to a method declaration (Strg+Left Mouse Click), it suggests me all 20 possible directories.

How can I set such dependencies or resolve the scope problem, so that each module is "capsuled" from the others?

Hope all of you understand my problem, if not please inform me.
Many thanks in advance for your help!

Best regards
DevFalko