Excel 导出打不开

$filename = iconv("UTF-8", "GB2312//IGNORE", '志愿者列表') . '-' . date('YmdHis') . '.xlsx';

        header('Content-Type: application/vnd.ms-excel');

        header('Content-Disposition: attachment;filename="'.$filename.'"');

        header('Cache-Control: max-age=0');

        header( 'Pragma: public' );

        header( 'Expires: 0' );

        header( 'Content-Encoding: none' );

        header( 'Cache-Control: must-revalidate, post-check=0, pre-check=0' );

        header( 'Cache-Control: public' );

        header( 'Content-Description: File Transfer' );

        header( 'Content-Transfer-Encoding: binary' );