How to force download unity asset bundle using php?

Question

I am downloading an asset bundle using the following code:

<?php
$file_url = "AssetBundle/bundle-numb";
header("Content-Type: application/zip");
header("Content-Disposition: attachment; filename=".basename($file_url));
readfile($file_url);
>?

However, only some bytes get downloaded and when I open the file I get an error saying

filesize(): stat failed for ....

When I try the same code for downloading other files it works fine, but not with asset bundles.

Asset bundles are LZMA compressed by default and I think the asset bundles do not have any file extentions.

Downloading works fine when I use the following directly in the browser:

http:XXXXXXXXXX.com/AssetBundle/bundle-numb 

Answer 1

I think i found the solution using php

<?php
$fileName = basename('bundle-rainbow');
$filePath = 'AssetBundles/'.$fileName;
if(!empty($fileName) && file_exists($filePath)){
    // Define headers
    header("Cache-Control: public");
    header("Content-Description: File Transfer");
    header("Content-Disposition: attachment; filename=$fileName");
    header("Content-Type: application/zip");
    header("Content-Length:".filesize($filePath));
    header("Content-Transfer-Encoding: binary");

    // Read the file
    readfile($filePath);
    exit;
}else{
    echo 'The file does not exist.';
    echo $fileName;
}
?>  
    // Read the file
    readfile($filePath);
    exit;
}else{
    echo 'The file does not exist.';
    echo $fileName;
}
?>