I can't tell you the number of times I've wanted/needed to have a cross reference utility for multiple module applications. I searched and was unable to find anything, so I'm writing my own. Right now you can click here to see the single program xref program do its thing on PHPNuke's mainfile.php module.

When all is said and done, this will be a programmer's toolbox to not only cross reference a single program, but to cross reference an entire project. It will (eventually) cross reference by both variable-name/line-number and line-number-variable-name. It will also include a cross referencing of all functions.