/**
*  无级递归分类
*  @param  int   $assortPid  要查询分类的父级id
*  @param  mixed  $tag     上下级分类之间的分隔符
*  @return string $tree    返回的分类树型结构结果 
*
*/
function recursiveAssort($assortPid, $tag = '')
{  
  $assort = M('goods_class')->where("class_pid = $assortPid")->field('class_id, class_name')->select();
  foreach ($assort as $value) {
    $tree .= '<option value="' . $value['class_id'] . '">' . $tag . $value['class_name'] . '</option>';
    $tree .= recursiveAssort($value['class_id'], $tag . ' ');
  }
  return $tree;
}