ERROR_MESSAGE_MAIN ERROR_MESSAGE_REASON on iPad and iPhone Safari

My website has a functionality of downloading excel sheet. I'm using PHPExcel library with Codeigniter to create the .xlsx sheet. It works fine almost everywhere but in iPad/ iPhone Safari. The following error covers the screen.

My code to download the file is following:

ob_end_clean();
$filename='attendance_list.xlsx';
header('Content-Type: application/vnd.ms-excel');
header('Content-Disposition: attachment;filename="'.$filename.'"'); 
header('Cache-Control: max-age=0');
$objWriter = PHPExcel_IOFactory::createWriter($this->excel, 'Excel2007'); 
$objWriter->save('php://output');

And i am calling the php function with this code via jquery and AJAX. Please provide me with the answers.