/**
  * update only one field
  *
  * @return void
  */
 public function update_field()
 {
     //init controller data
     $this->extensions->hk_InitData($this, __FUNCTION__);
     $this->loadLanguage('design/content');
     $this->acm = new AContentManager();
     if (!$this->user->canModify('listing_grid/content')) {
         $error = new AError('');
         return $error->toJSONResponse('NO_PERMISSIONS_402', array('error_text' => sprintf($this->language->get('error_permission_modify'), 'listing_grid/content'), 'reset_value' => true));
     }
     $allowedFields = array('title', 'description', 'keyword', 'store_id', 'sort_order', 'status', 'parent_content_id');
     if (isset($this->request->get['id'])) {
         //request sent from edit form. ID in url
         foreach ($this->request->post as $field => $value) {
             if (!in_array($field, $allowedFields)) {
                 continue;
             }
             if ($field == 'keyword') {
                 if ($err = $this->html->isSEOkeywordExists('content_id=' . $this->request->get['id'], $value)) {
                     $error = new AError('');
                     return $error->toJSONResponse('VALIDATION_ERROR_406', array('error_text' => $err));
                 }
             }
             if ($field == 'sort_order') {
                 // NOTE: grid quicksave ids are not the same as id from form quick save request!
                 list($void, $parent_content_id) = explode('_', key($value));
                 $value = current($value);
             }
             $this->acm->editContentField($this->request->get['id'], $field, $value, $parent_content_id);
         }
         return null;
     }
     //request sent from jGrid. ID is key of array
     foreach ($this->request->post as $field => $value) {
         if (!in_array($field, $allowedFields)) {
             continue;
         }
         // NOTE: grid quicksave ids are not the same as id from form quick save request!
         list($parent_content_id, $content_id) = explode('_', key($value));
         $this->acm->editContentField($content_id, $field, current($value), $parent_content_id);
     }
     //update controller data
     $this->extensions->hk_UpdateData($this, __FUNCTION__);
 }