Generation of Class Diagram from XMI

Question

Situation

I have a PHP project with lots of classes with lots of relationships in lots of folders following the Zend Naming Convention.

I use the NetBeans IDE 7.

Answer 1

(Edit : This answer is an alternative for people that want to generate UML class diagram from a PHP project, it doesn't explains how to read XMI files)

Goal

I need to see a graphical representation of the class relationships, possibly in varying depths and varying degrees of complexity. Also, it would be nice if the classes in the diagram are clickable. I do not necessarily need to generate documentation.

If your goal was to generate a class diagram from a PHP project, I found a better solution than use PHP_UML. What you probably want is BoUML, with this software, you can select a PHP project folder and reverse engineering it. Then create a class diagram. When you drag&drop the class on it, the relations are there unlike AlgoUML (If I'm not wrong). XMI files are no longer useful in this case.