public function deleteAction()
 {
     $this->_helper->viewRenderer->setNoRender();
     $this->_helper->getHelper('layout')->disableLayout();
     if ($this->getRequest()->isPost()) {
         $id = $this->_getParam('id', 0);
         $purchaseorder = new Purchases_Model_DbTable_Purchaseorder();
         $purchaseorder->deletePurchaseorder($id);
         $positions = $this->getPositions($id);
         $positionsDb = new Purchases_Model_DbTable_Purchaseorderpos();
         foreach ($positions as $position) {
             $positionsDb->deletePosition($position->id);
         }
     }
     $this->_flashMessenger->addMessage('MESSAGES_SUCCESFULLY_DELETED');
 }