New Post: Laravel with phpExcel

I just using composer install phpExcel in Laravel and follow its example, however,the first sample 01simple-download-xlsx will caused MS Excel 2010 error message "Excel cannot open the file myfile.xlsx because the file format or file extension is not valid" when open in Laravel View while the download file could be read flawless.
Here is my setup:
controller:

return View::make('simpleDownloadXlsx');

View:

<?php
/** Error reporting */
ob_start();
error_reporting(E_ALL);
ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);
date_default_timezone_set('Asia/Taipei');

if (PHP_SAPI == 'cli')
    die('This example should only be run from a Web Browser');

/** Include PHPExcel */
$pRoot=dirname(dirname(dirname(__FILE__))).'/vendor';
require_once $pRoot.'/phpoffice/phpexcel/Classes/PHPExcel.php';


// 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', 'TW');

// 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 (Excel2007)

//$file = "myfile.xlsx";
header('Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
header('Content-Disposition: attachment;filename="01simple.xlsx"');
header('Cache-Control: max-age=0');
ob_clean();
flush();
//readfile($file);
$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
$objWriter->save('d:/l4/test/01simple.xlsx');
ob_end();
exit;

A user has exactly same issue and fixed by adding:

ob_clean()
flush()

But no lucky in Laravel.
Any help/guide would be appreciated.