Practical Php Testing exercises

As you probably know there is a Creative Commons licensed ebook available on this blog, Practical Php Testing.
Tomaž Muraus wrote to me yesterday about solving the TDD exercises contained in the various chapters:

I had some time during the past few days so I read your book and solved the exercises found in the book.
I'm pretty sure not all of my solutions are the best and some could probably be improved / changed so I decided to create a Github repository with my solutions (http://github.com/Kami/practical-php-testing-exercise-solutions) so others can fork it and improve / refactor my solutions.

I hope you can find these examples useful, but try not to read a solution before actually trying to solve an exercise. I have not proof read this code but it seems that its quality is good. There is always room for improvement, especially in the stubs section of the tests, and in refactoring of the production code.