The registry object

The registry object is a singleton which acts through all the application like a singleton dictionary.
Basically it has a setter and a getter methods by which other objects my create new registry properties. Since the registry is shared by all objects, each of them has access to the properties setted by the others through the __get method. Hence the registry is a global dictionary (actually an associative array, but I'll call it dictionary since it's what it represents) used to store public and sharable properties and objects.