Zend-Option Group in Zend_Form_Element_Multiselect

 $techDoc = new Zend_Form_Element_Multiselect(‘technical_doc’);  
 $techDoc->setLabel(‘Technical Documents’)  
 ->setMultiOptions(array(“Option Group 1″ => array(“option1″,”option2″,”option3″),  
 “Option Group 2″=>array(“option1″,”option2″,”option3″)));