/**
  * 构造用户组
  *
  * @param string $gid
  * @return string
  */
 private function _buildGids($gid)
 {
     $gidOptions = '<option value="-1" ' . Pw::isSelected($gid == -1) . '>全部用户组</option>';
     $gidOptions .= '<option value="0" ' . Pw::isSelected($gid == 0) . '>会员组</option>';
     /* @var $groupDs PwUserGroups */
     $groupDs = Wekit::load('usergroup.PwUserGroups');
     $groups = $groupDs->getClassifiedGroups();
     if (!$groups) {
         return $gidOptions;
     }
     $types = $groupDs->getTypeNames();
     unset($types['member']);
     foreach ($types as $_k => $_v) {
         if (!isset($groups[$_k])) {
             continue;
         }
         $option = '<optgroup label="' . $_v . '">';
         foreach ($groups[$_k] as $_item) {
             $option .= '<option value="' . $_item['gid'] . '" ' . Pw::isSelected($gid == $_item['gid']) . '>' . $_item['name'] . '</option>';
         }
         $gidOptions .= $option;
     }
     return $gidOptions;
 }