LampCMS open source XSLT based content management

All classes are documented very well.

The site is event-driven. Events are fired similar to how events work in browser model. You can write up a new extension that will subscribe to any specific event and then do its thing when such event fires. For example, we have events 'onUserLogin', 'onProfileUpdate', 'onLogout', 'onNewReply', and many more... Or yes, our event system implements SplSubject Interface
and if you want to subscribe to the events all you have to do is make sure that your class implements SplObserver interface.

Good form validation with using form rules. We use HTML_QuickForm pear class, slightly modified (improved), so if you are familiar with this class it will be very easy for you to create new forms and add any form validation rules (like required fields, validate email address, validate alphanumeric only, etc.)

We use many SPL classes, like SPL fileinfo to represent a file, ArrayObject to represent many arrays and objects, many of our objects implement serializable interface. Basically if you are familiar with SPL objects, it will be easy for you to understand the design of many of our classes. If you are not familiar with SPL but always wanted to learn how to use theme, then working on our project is going to make this easy for you you will become an expert in using SPL in no time!

Some event types also bubble up, just like events in javascript.

With events it's easy to hook to the objects. For example, you can write a spam filter that listens to 'onNewReply', then examines the contents of the reply and if any spam words are found it will issue
a cancelEvent() call, so that the reply will never be added to the database.

An excellent logging system makes debugging and development very easy. You can add a simple line:
$this->log('something happened); anywhere in your script.

The logger will automatically extract the class name and line number of this line, so in your log you will see a timestamp, class, line as well as your message.

This means you don't have to add __METHOD__.' line: '.__LINE__ to every one of your log messages, this is done automatically for you.

Also admin is automatically notified by email every time the message is added to log that contains the work 'Error', so you may log some problematic events this way:
$this->log('Error: uploaded file could not be saved');

This message will be added to log and a copy of it will be sent to admin.
We even have a javascript logging console. You can use logging in any of your own javascripts. Just add
$L('got response ' + response);

This will immediately appear on logging console (small draggable panel on the page)

This javascript logging panel is only visible to developers (you must add your ip address to special file)

Lastly there is an sql query logging. All SQL queries on the site go through the Database class which logs query as well as time before and time after the query, so the time (in milliseconds) is known for every sql query. This data is then dumped to the bottom of a page. Again, this will be visible ONLY to developers and is only activated when request comes from one of the ip addresses added to developer's Ips)

All these things makes developing with Lampcms an unusually pleasant experience.