In this two-part chapter, you were introduced to the computer science theory of a Finite State Machine (FSM). You learned how it is defined, what separates it from other abstract machines, and how it is useful. You met the theory of any FSM and saw how it translates into the simple example of a Reverse Polish Notation (RPN) Calculator. You saw the code of a working example of the RPN Calculator dissected in detail, paying close attention to how the PEAR class FSM had been used in its implementation.
You then looked at configuration files. You examined why they are useful in your application, saw the various flavors available, and learned how to best parse them We also covered the do's and don'ts of configuration file implementation.
This concludes Part III of this book. By now, you've built up a complete toolkit of code and techniques to deploy in your own applications. In Part IV, you'll look at how to assemble a useful, real-life application using these tools, and examine the optimal way to manage projects of that nature.