observer/notifier the "base" class

In the API turtorial it is explained that every class that want to make use of observer/notifier system has to extend the "base"
class. However I cannot see how this can work. Maybe it is because I am a C++ guru and not a PHP. The problem as I see it is that we get different instances of the "base" class for every instance of observer or notifier class. Therefore the following observerclass will never get the notification from the shopping_cart class.

The documentation is buggy.

Your c'tor should instead say

$_SESSION['cart']->attach($this, array('NOTIFIER_CART_ADD_CART_END'));

for cart stuff. The cart object maintains a list of observers and calls them when
the notify() method is called for the events they have registered for. Similarly, zco_notifier, etc.

Scott