If you are looking for an algorithm that will allow you to download (force download) a big file, may this one will help you.
$filename = "file.csv";
$filepath = "/path/to/file/" . $filename;
// Close sessions to prevent user from waiting until
// download will finish (uncomment if needed)
//session_write_close();
set_time_limit(0);
ignore_user_abort(false);
ini_set('output_buffering', 0);
ini_set('zlib.output_compression', 0);
$chunk = 10 * 1024 * 1024; // bytes per chunk (10 MB)
$fh = fopen($filepath, "rb");
if ($fh === false) {
echo "Unable open file";
}
header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="' . $filename . '"');
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . filesize($filepath));
// Repeat reading until EOF
while (!feof($fh)) {
echo fread($handle, $chunk);
ob_flush(); // flush output
flush();
}
exit;