PHP ดาวน์โหลดไฟล์ผ่าน browser หลังจาก POST

$filename = '/folder/DEMO.TXT';
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename='.basename($filename));
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . filesize($filename));
readfile($filename);
exit;

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