Phalcon Select field sort options

Hello How to sort, items in select field ? Because i have prepared the field and added options into it, but the empty value is last ....

$plan = new \Phalcon\Forms\Element\Select('plan',null,array(
    'useEmpty' => true,
    'emptyText' => $lang->translate("Vyberte tarif pro zařízení."),
    'emptyValue' => null
));