phpexcel导出文件或者文件扩展名不一致 或 导出的文件或文件扩展名无效

此情形在在本机没发现，服务器上报错。解决方式很简单

ob_end_clean();//清除缓冲区,避免乱码(增加此行即可)

header(“Pragma: public”);
header(“Expires: 0”);
header(“Cache-Control:must-revalidate, post-check=0, pre-check=0”);
header(“Content-Type:application/force-download”);
header(“Content-Type:application/vnd.ms-execl”);
header(“Content-Type:application/octet-stream”);
header(“Content-Type:application/download”);;
header(‘Content-Disposition:attachment;filename=’.$file_name.’.xls’);
header(“Content-Transfer-Encoding:binary”);
$write->save(‘php://output’);