echo $this->Form->create('Firm', array('url' => array('controller' => 'firms', 'action' => 'setcategories')));
    echo $this->Form->input('Firm.id', array('type' => 'hidden', 'value' => $firm['Firm']['id']));
    echo $this->Form->input('Category', array('type' => 'select', 'multiple' => 'checkbox', 'options' => $categories));
    echo $this->Form->end('Speichern');