While exporting to XLS output is garbage even with correct headertypes - phpexcel

Question

I have tried some solutions provided in other questions about exporting to Excel sheet using PHP,still not working.Also I referred to PHPExcel library examples still stuck.
Here's my code.
<?php
ob_start();
require_once 'Classes/PHPExcel.php';
$objPHPExcel = new PHPExcel();
$objPHPExcel->getProperties() ->setCreator("MeritTrac")
->setTitle("PHPExcel Test document")
->setSubject("PHPExcel Subject")
->setDescription("This is generatred by PHPExcel");
$objPHPExcel ->setActiveSheetIndex(0)
->setCellValue('A1','Hello')
->setCellValue('B1','Test')
->setCellValue('C1','Color')
->setCellValue('D1','World');
$objPHPExcel ->setActiveSheetIndex(0)
->setCellValue('A4','Miscellaneous Glyph')
->setCellValue('A5','ífá');
$objPHPExcel ->setActiveSheetIndex(0);
header('Content type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
//header('Content type:application/vnd.ms-excel');
header('Content disposition: csv;filename="download.xlsx"');
header('Cache-Control: max-age=0');
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');
echo "Test print";
$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
$objWriter->save('php://output');
exit;
?>
<?php
ob_end_flush();
?>
Output:
http://imgur.com/a/5AsWF
Please find what I am missing coz this code gives me garbage output.