php 二维数组 转字符串 implode 方便 mysql in 查询

      foreach($gid_list as $k=>$v){
        $gid_array[] = $v['gid'];
      }
      if(count($gid_array)<2){
        $gid_str = $gid_array['0'];
      }else{
        $gid_str = implode(',',$gid_array);
      }