Cytat
Since regex patterns are not easily reversed, you will need to prepare a reverse URL if you wish to use a URL helper or even an assemble method of this class. This reversed path is represented by a string parsable by sprintf() and is defined as a fourth construct parameter:
<?php $route = new Zend_Controller_Router_Route_Regex( 'archive/(d+)', 'archive/%s' ); ?>
rozumiem ogolne zastosowanie tej klasy, ale nie bardzo wiem o co chodzi z 4tym parametrem, czy mógłby ktoś wyjaśnić na przykładzie