Help comprehending how the following framework fits together:

[leadicemelf]

I am just getting into OOP and framework design. I have started by using the following three tutorials;http://net.tutsplus.com/tutorials/php/creating-a-php5-framework-part-1/http://net.tutsplus.com/tutorials/php/create-a-php5-framework-part-2/http://net.tutsplus.com/tutorials/php/create-a-php5-framework-part-3/This is the first framework I have tried to work with and because the tutorial is not aimed at complete novices I am finding myself having to reverse-engineer the code to see how everything works. The problem is I'm stuck.First, I understand the basic concepts of the framework including the directory structure.Second, I understand what the registry and database class are for (although I don't fully understand every function within them just yet). My problem comes with the index.php, template.class.php and page.class.php files. I broadly know what each should do (although further explanation would be nice!) but I do not get how they fit together i.e. how does the index page interact with the template and page objects to actually produce the page that is displayed. I especially cannot work out in what order everything is called. The index appears to me as:

• require registry class
• create instance of registry (don't quite get this bit - easier way to access database?)
• store the database and template objects
• creates new connection from the stored database object
• choose the skin for the page

Then, and here is where I get lost:

• build actual page via buildFromTemplates function (which I can't get my head round)
• cache a database query
• assign tab (i'm completely lost as to what a tag is!)
• set page title
• display content

Can anyone help break this down for me? I tried Zend before this but it was far too complicated, this one is more accessible but as you can still has me stumped (although I have started to understand objects FAR more by trying). Thanks in advance.