I have written a small script to generate class dependency graphs out of a bunch of php files last week. I needed this for a project I am currently working on.
First of all I want to publish this script, free to use for anybody to whom this might be useful. You can get the complete script at the end of this post.
I have been told that doxygen can create something similar to my graphs. This graphs didn't completey satisfy me, but you can take a look there, if you aren't happy with the representation my script generates.
After the script did what I wanted it to, I decided to create classgraphs of the ez Components just for fun. After looking on some of these I realized that they might be useful or at least quite interesting to other people around the net.
If you are interested in the scripts that generate this graphs just checkout its svn repository:
There you will find a slightly modified version of the mentioned script, which will create the shown graphs for you based on the current ezc trunk.