i use this in my Form:
$this->add(array(
'type' => 'Zend\Form\Element\Select',
'name' => 'county',
'registerInArrayValidator' => false,
'attributes' => array(
'id' => 'county',
'options' => array(
//'null'=>'[Select county]',
),
),
'options' => array(
'label' => 'county',
),
));
and set value county field with js. after validation, i get error : haystack option is mandatory