PHPExcel error when opening downloaded file error "incorrect file format" - zend-framework

Question

I'm creating an Excel report containing UTF-8 encoded data using PHPExcel on Zend. When I'm downloading and trying to open it in Excel it works on local environment but I'm getting the following Error: "Incorrect file format" from live sever/production. Any help / references would be appreciated.
here is a code i used to download xls file:
public function getCsv($data, $filename = false)
{
/**
* generate a file name using unixTimeStamp
* #var string $tmpfname
*/
if ($filename)
{
$tmpfile = "/tmp/".$filename. "-". date('Y-m-d_H:i:s') . ".csv";
$name = str_replace(' ','',$filename)."-".date('Y-m-d_H:i:s') . ".xls";
}
else
{
$tmpfile = "/tmp/report". "_". date('Y-m-d_H:i:s') . ".csv";
$name = "report-".date('Y-m-d_H:i:s') . ".xls";
}
/**
* open Temporary file name in write mode
* #var object $fp
*/
$fp = fopen($tmpfile, "w");
/**
* foreach datas write to csv
*/
foreach ($data as $fields)
fputcsv($fp, $fields, ',', '"');
/**
* close file
*/
fclose($fp);
try
{
$objReader = PHPExcel_IOFactory::createReader('CSV');
$objPHPExcel = $objReader->load($tmpfile);
$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel5');
//set Header Content Type as application/csv
header("Content-Type: application/vnd.ms-excel; charset=utf-8");
header("Content-Disposition: attachment; filename=$name");
$objWriter->save('php://output');
}
catch (Exception $e)
{
echo $e->getMessage();
}
exit;
}

Answer 1

You must use this line before saving :
ob_end_clean();