The decision tree application is currently a work-in-progress. The main source files can be downloaded here: Source Files. The current demo is non-functional and only shows a subset of the application, which will be developed in the upcoming weeks: Demo Application (Work in progress)
The following are my responses to a series of simple PHP problems (attached in the Word File). I needed to review Doyle (2010) chapters 9 and 10 which cover form submission and session variables in order to complete these exercises. I also leaned on chapter 18 which goes into depth on regular expressions to assist with pattern recognition.