Adding another URL into a download script - php

Question

I have a video streaming website which also allows users to download videos. This runs over a download script that loads the videos id on the server and initiates a direct file transfer.
Now I want to put another URL in front of it instead of having the direct file transfer. I tried to make a mod_rewrite rule, but it causes a loop and redirects on that URL forever. Its a link shortening service which allows monetarization.
So, how do I archieve this? Is it possible to archieve it with a mod_rewrite rule?
Trying the mod_rewrite rule, realizing I can't change the base_url variable in PHP because it would not find the file anymore.
$vid = intval($_GET['id']);
$label = intval($_GET['label']);
$sql = "SELECT * FROM video WHERE VID = ".$vid." LIMIT 1";
$rs = $conn->execute($sql);
$formats = $rs->fields['formats'];
$server = $rs->fields['server'];
$formats_arr = explode(',', $formats);
if ($server != '') {
$sql = "SELECT * FROM video v, servers s WHERE v.VID = ".$vid." AND v.server = s.video_url LIMIT 1";
$rs = $conn->execute($sql);
$video_root = $rs->fields['video_url'];
}
if (!$video_root) {
$video_root = $config['BASE_DIR']."/media/videos";
}
foreach ($formats_arr as $format) {
$f = explode('.', $format);
if ($label == $f[1]) {
if ($f[0] >= 481) {
$condition = $new_permisions['hd_downloads'];
} else {
$condition = $new_permisions['sd_downloads'];
}
$file = $video_root.'/h264/'.$vid.'_'.$f[1].'.'.$f[2];
$file_name = $vid.'_'.$f[1].'.'.$f[2];
break;
}
}
if ($condition == 1) {
ini_set('memory_limit', '-1');
if (!$server) {
if (file_exists($file) && is_file($file) && is_readable($file)) {
$conn->execute("UPDATE video SET download_num = download_num+1 WHERE VID = ".$vid." LIMIT 1");
#ob_end_clean();
if(ini_get('zlib.output_compression')) {
ini_set('zlib.output_compression', 'Off');
}
header('Content-Type: application/force-download');
header('Content-Disposition: attachment; filename="'.basename($file).'"');
header('Content-Transfer-Encoding: binary');
header('Accept-Ranges: bytes');
header('Cache-control: private');
header('Pragma: private');
header('Expires: Mon, 26 Jul 1997 05:00:00 GMT');
header('Content-Length: ' .filesize($file));
readfile($file);
exit();
} else {
VRedirect::go($config['BASE_URL']. '/error');
}
} else {
$conn->execute("UPDATE video SET download_num = download_num+1 WHERE VID = ".$vid." LIMIT 1");
header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename='.basename($file));
header('Content-Transfer-Encoding: chunked');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
$stream = fopen('php://output', 'w');
$ch = curl_init($file);
curl_setopt($ch, CURLOPT_READFUNCTION, function($ch, $fd, $length) use ($stream) {
return fwrite($stream, fread($fd, $length));
});
The download button should open URL/download.php with my link shortener URL in front of it, so it will load and redirect to the file download URL.