The QaFoo team has made available a tool they've created to track changes in PHP projects, the QaFoo Changetrack tool.
Since quite some time I've talked to people about the idea for a tool that tracks changes in the classes and methods of your PHP project in order to detect which entities are changed most frequently, which are often affected bugs and other statistics. After some hacking, we are now making it available on Github.
The tool includes a few commands including one that analyzes the project you point it at (and makes an XML defining its changesets) and another that provides a report of how often a certain method is involved in a change. The post includes an example using the Twig Github repository noting that, because of the analysis being done on each checkout, can take quite a while depending on the age of the project.