The static registry is an instance of the class Zend_Registry.
If you want to add functionality to the registry, you should
create a class that extends Zend_Registry and
specify this class to instantiate for the singleton in the static registry.
Use the static method setClassName() to specify
the class.
Note
The class must be a subclass of Zend_Registry.
Example 675. Example of Specifying the Singleton Registry's Class Name
<?php
Zend_Registry::setClassName('My_Registry');
Zend_Registry::set('index', $value);
The registry throws a Zend_Exception if you attempt to set the
classname after the registry has been accessed for the first time.
It is therefore recommended that you specify the class name for your
static registry in your application bootstrap.