This is the source code used in my presentation on the Open / Closed Principal to the GTAPHP Meetup Group (http://meetup.gtaphp.org/events/45215312/). You can see the slides and my notes on how I made the edits in this repository on my blog here:
http://blog.vicmetcalfe.com/2012/01/04/solid-php-code-smells-part-2-open-closed-principal/
Please post any comments, criticisms or suggestions there. I look forward to your feedback!
The repository preserves the history of the code as I went through the presentation, so you can go back to the initial commit and view each set of changes as I refactored the code.
The code we worked on follows the REST architecture for web services and provides services for maintaining a list of people called 'users'. We start with that and then deal with a change request to handle book recommendations by users. This triggers the bulk of the refactoring in the presentation. Finally we get another change request to add support for XML encodings as well as JSON for another round of refactoring.
Please excuse some of the crappy things you'll find in this code, like minimal test code and poor handling of error conditions and edge cases. I tried to keep it as simple as possible so we could get through as much as possible in an hour.
I used a product called CodeBox which is a snippet manager for Mac to avoid wasting time typing blocks of code during the presentation. The presenter's notes on my blog mention CodeBox shortcuts which begin ocp and which expand into the full snippet when typed. These can be found in OCP.cbxml for those of you who have CodeBox and want to follow along.
This is my own knockout.js plugin which simplifies using REST services with knockout. It has a long way to go before I'd really be happy to release it. For now it is awkward with master / detail relationships. It pushes you to put all your models in a flat list like the sql tables behind them even when it would be better to roll the detail data into the master's model. I've started work on a big update which addresses that problem, but you won't find that here. Also I haven't written any documentation for it. When I've addressed those two issues I'll publish it separately. Until then, use it at your own peril!