使用 PHPExcel 生成 Excel 失败，因为文件格式或文件扩展名无效

我正在使用CakePHP和PHPExcel来生成excel文件，我可以生成文件并将它们保存在服务器中并且它们可以工作，但是当我使用 $objWriter->save('php://output'); 并打开下载的文件时，我file cannot open file because the file format or file extension is not valid.

我什至在脚本开头使用了ob_start();，并在保存之前使用了ob_end_clean();，但我仍然收到相同的错误

这是我的代码(这段代码来自 PHPExcel 的示例，我只是添加了 ob_start 和 ob_end_clear(：

<?php
ob_start();
App::import('Vendor', 'PHPExcel');
error_reporting(E_ALL);
ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);
date_default_timezone_set('Europe/London');
if (PHP_SAPI == 'cli')
    die('This example should only be run from a Web Browser');
// Create new PHPExcel object
$objPHPExcel = new PHPExcel();
// Set document properties
$objPHPExcel->getProperties()->setCreator("Maarten Balliauw")
        ->setLastModifiedBy("Maarten Balliauw")
        ->setTitle("Office 2007 XLSX Test Document")
        ->setSubject("Office 2007 XLSX Test Document")
        ->setDescription("Test document for Office 2007 XLSX, generated using PHP classes.")
        ->setKeywords("office 2007 openxml php")
        ->setCategory("Test result file");

// Add some data
$objPHPExcel->setActiveSheetIndex(0)
        ->setCellValue('A1', 'Hello')
        ->setCellValue('B2', 'world!')
        ->setCellValue('C1', 'Hello')
        ->setCellValue('D2', 'world!');
// Miscellaneous glyphs, UTF-8
$objPHPExcel->setActiveSheetIndex(0)
        ->setCellValue('A4', 'Miscellaneous glyphs')
        ->setCellValue('A5', 'éàèùâêîôûëïüÿäöüç');
// Rename worksheet
$objPHPExcel->getActiveSheet()->setTitle('Simple');

// Set active sheet index to the first sheet, so Excel opens this as the first sheet
$objPHPExcel->setActiveSheetIndex(0);

// Redirect output to a client’s web browser (Excel5)
header('Content-Type: application/vnd.ms-excel');
header('Content-Disposition: attachment;filename="01simple.xls"');
header('Cache-Control: max-age=0');
// If you're serving to IE 9, then the following may be needed
header('Cache-Control: max-age=1');
// If you're serving to IE over SSL, then the following may be needed
header('Expires: Mon, 26 Jul 1997 05:00:00 GMT'); // Date in the past
header('Last-Modified: ' . gmdate('D, d M Y H:i:s') . ' GMT'); // always modified
header('Cache-Control: cache, must-revalidate'); // HTTP/1.1
header('Pragma: public'); // HTTP/1.0
$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel5');
ob_end_clean();
$objWriter->save('php://output');
exit;

这是生成的文件：https://mega.co.nz/#!RZFURbTA!DaGVv1NzRZn3VGq0FSf57nQTKiB--4sq2udj2HkTq2U