Disable select option in Zend Form

We can do that using the setAttribs property in the Zend Form Element

Ex:
$roles = new Zend_Form_Element_Select("roles");
$roles->setLabel("Roles");
$roles->addMultiOptions(array('1' => 'Admin', '2'=>'Group Admin','3'=>'User'));
suppose if we want to set it disable if the user is 'User'.
if($roleValue > 2)
$roles->setAttribs(array('disabled'=>'disabled'));