phpexcel为什么无法生成xlsx文件

header('Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
header('Content-Disposition: attachment;filename="fee_detail.xlsx"');
header('Cache-Control: max-age=0');

$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
$objWriter->save( 'php://output');

header('Content-Type: application/vnd.ms-excel');
header('Content-Disposition: attachment;filename="fee_detail.xls"');
header('Cache-Control: max-age=0');

$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel5');
$objWriter->save('php://output');