下载不适用于IE8

Question

我使用了以下代码来下载pdf文件，但它在IE8中不起作用。它在Firefox中运行良好。

header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="'.$fileName.'"');
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . filesize($fileName));
ob_clean();
flush();
readfile($fileName);

输出空白屏幕。