commit 0006: Added libs/View.php for displaying our view page and Controller are updated to call the view class methods. 

View.php class render method is responsible for rendering the View/xzyFolder/xyz.php file. 

Controllers are creating a new instance of View class and calling the rendering method.
commit 0007: Added libs/BaseController.php as the parent class for all controllers. 

If i see commit 0006, each controller classes had a private field view, which i was instantiating in the constructor. Since each controller class is going to use this field why dont we put it in a parent class and then call the parent constructor which instantiates the field. Now the view field is usable in multiple files. 

The BaseController has an abstract method index() as we want all the child controllers to implement this method. In case user does not provide the full url, then we will call the default mehtod i.e. index. Since we have an abstract method in the class, the class itself needs to be declared as abstract. 

This is an example of inheritance where many classes extends a parent class.