public function init()
 {
     parent::init();
     $element = new Zend_Form_Element_Select('hm_bed_id');
     $element->setLabel('Bed (bxl) in cm')->addMultiOption('', '...')->setRequired(true);
     foreach (Model_Hm_Bed::listAll()->execute() as $bed) {
         $element->addMultiOption($bed->id, $bed->width . 'x' . $bed->length);
     }
     $this->addElement($element);
     $element = new Zend_Form_Element_Text('amount');
     $element->setLabel('Aantal')->setFilters(array(array('int')))->setValidators(array(array('digits')))->setRequired(true);
     $this->addElement($element);
     $element = new Zend_Form_Element_Submit('submit_bed_amount');
     $element->setAttrib('class', 'submit')->setLabel('Verwerken');
     $this->addElement($element);
     $this->addDisplayGroup(array('hm_bed_id', 'amount'), 'Bed', array('legend' => 'Bed'));
     $this->addDisplayGroup(array('submit_bed_amount'), 'submit', array('class' => 'submit'));
     parent::bhvkDecorators();
     parent::bhvkDecorateSubmit('submit_bed_amount');
 }