Are there any more generic tools that can "compile" or basically merge multiple PHP files into a single file based on includes and autoloading classes? I'm thinking of something similar to Doctrine's compiling functionality or the compiling that many of the major JS frameworks do for "production" sites to lighten the file size and improve performance.
Before writing a script to do it myself, I just want to find out if anything worth looking at already exists (Google hasn't been much help so far).
Edit: I've actually written a blog post about the .phar archive format and am very excited about that. I was actually more concerned about performance, but it sounds like merging files would not yield any benefit.
Does anyone have any real data that might suggest the performance gain (or lack thereof) from merging multiple scripts into a single file?