Everyone who understands PHP but don't Java and wants to understand basics of refactoring in practise form.
If you chose path enlightenment into refactoring thru reading Martin Fowler's book "Refactoring Improving the Design of Existing Code" you would noticed that members classes were written in Java and unfamiliar syntax may distract attention from learning about refactoring patterns.
May will be helpful for novice programmers.
The project reflects the process of refactoring into commits. Just go back to whatever you want commit actual reading of the book. Play with code by execute "./run" from console.