I'm using Zend_Application and I had to extend Zend_Navigation_Page so I've created my custom class Qengine_Navigation_Page and then in configuration file of my application I've set 'defaultPageType' to 'Qengine_Navigation_Page'. I was very confused, why all page in the main container are instances of Zend_Navigation_Page, not of mine custom class. So I've done my homework and found out, that this code 'Zend_Navigation_Page::setDefaultPageType($options['defaultPageType']);' should be invoked before building the tree from 'pages' options in configuration file, so the type of the Page can be changed.

That's how it should be done:

public function init()
    {
        if (!$this->_container) {
            $options = $this->getOptions();
            
            if(isset($options['defaultPageType'])) {
                Zend_Navigation_Page::setDefaultPageType($options['defaultPageType']);                
            }
            
            $pages = isset($options['pages']) ? $options['pages'] : array();
            $this->_container = new Zend_Navigation($pages);
        }

        $this->store();
        return $this->_container;
    }