I'm using PHPExcel for exporting a report.
It's gave me an error when I run it on internet (using PHP 5.6)..
But, when I'm test on my localhost, it's fine. Works perfectly (using PHP 5.4.31)
Here's my code

function downloadExcelBrand($brand,$tglAwal,$tglAkhir)
{

    $this->load->library('php_excel');

    $objPHPExcel = new PHPExcel(); 
    // print_r($objPHPExcel);die();
    $objPHPExcel->setActiveSheetIndex(0);

    $objPHPExcel->getActiveSheet()->SetCellValue('A1', "Concept");
    $objPHPExcel->getActiveSheet()->SetCellValue('B1', $brand);

    $objPHPExcel->getActiveSheet()->SetCellValue('A2', "Period");
    $objPHPExcel->getActiveSheet()->SetCellValue('B2', $tglAwal." to ".$tglAkhir);

    $objPHPExcel->getActiveSheet()->SetCellValue('A5', "Boutique");
    $objPHPExcel->getActiveSheet()->SetCellValue('B5', "Q1");
    $objPHPExcel->getActiveSheet()->SetCellValue('C5', "Q2");
    $objPHPExcel->getActiveSheet()->SetCellValue('D5', "Q3");
    $objPHPExcel->getActiveSheet()->SetCellValue('E5', "Q4");
    $objPHPExcel->getActiveSheet()->SetCellValue('F5', "BBC Score");

    $data = $this->surveymodel->getDataLaporanBrand($brand,$tglAwal,$tglAkhir);
    // print_r($data);die();
    $i = 5;
    foreach ($data as $index=>$value) {
        // print_r($data[$index+1]);die();
        if( $index%4 == 0){
            $i++;
            // print_r($value["Score"]);print_r($value['TotalData']);die();
            $AvgQ1 = $value["Score"] / $value['TotalData'];
            // print_r($AvgQ1);die();
            $AvgQ2 = $data[$index+1]["Score"]/$data[$index+1]['TotalData'];
            $AVGQ3 = $data[$index+2]["Score"]/$data[$index+2]['TotalData'];
            $AvgQ4 = $data[$index+3]["Score"]/$data[$index+3]['TotalData'];
            $BSC = $AvgQ1+$AvgQ2+$AVGQ3+$AvgQ4;

            $objPHPExcel->getActiveSheet()->SetCellValue('A'.$i, $value["boutiqueID"]);
            $objPHPExcel->getActiveSheet()->SetCellValue('B'.$i, $AvgQ1);
            $objPHPExcel->getActiveSheet()->SetCellValue('C'.$i, $AvgQ2);
            $objPHPExcel->getActiveSheet()->SetCellValue('D'.$i, $AVGQ3);
            $objPHPExcel->getActiveSheet()->SetCellValue('E'.$i, $AvgQ4);
            $objPHPExcel->getActiveSheet()->SetCellValue('F'.$i, $BSC);
        }
    }

    // Instantiate a Writer to create an OfficeOpenXML Excel .xlsx file
    $objWriter = new PHPExcel_Writer_Excel2007($objPHPExcel); 
    // Write the Excel file to filename some_excel_file.xlsx in the current directory
    header('Content-type: application/vnd.ms-excel');
    // It will be called file.xls
    header('Content-Disposition: attachment; filename="Report_By_Brand.xlsx"');
    // Write file to the browser
    $objWriter->save('php://output');
}

the weird things happen when I remove the $objWriter->save('php://output'); code. It's asking for saving the excel, but the excel file can't be open because it's corrupted..

• EDIT
• The error is

This site can’t be reached The webpage at http://my-link-in-here might be temporarily down or it may have moved permanently to a new web address. ERR_INVALID_RESPONSE

• UPDATE
• I try to add ob_end_clean(); or ob_clean(); before $objWriter->save('php://output'); and it saving the Excel, but I can't open it because Excel says "File Format or File Extention is not valid".
• I try to change the xlsx extension to xls on filename properties, and the Excel now can be opened. But It shows php error Message: ob_end_clean(): failed to delete buffer. No buffer to delete
• I try to keep the extension but I deleted the ob_end_clean(); , and the error comes again..
• Solution :
• I changed the code to be Excel5 like this

$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel5');
header('Content-Type: application/vnd.ms-excel');
header('Content-Disposition: attachment;filename="userList.xls"');

And it works like champion. Anyone can make a explanation ? I will give the solution to the one who can make the explanation