Recommends headers for an OfficeOpenXML .docx file
// Redirect output to a client’s web browser (.docx)
header('Content-Type: application/vnd.openxmlformats-officedocument.wordprocessingml.document');
header('Content-Disposition: attachment;filename="kikou2.docx"');
header('Cache-Control: max-age=0');
// If you're serving to IE 9, then the following may be needed
header('Cache-Control: max-age=1');
// If you're serving to IE over SSL, then the following may be needed
header ('Expires: Mon, 26 Jul 1997 05:00:00 GMT'); // Date in the past
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'); // HTTP/1.0
paying particular attention to the Content-Type
heading