Uploading file using PHP Curl to another server

Question

I am trying currently to accomplish the following:

I have a server, where a PHP-Application is running on. I have to extract some files and send them to another server (Django) with a POST request. I am trying to accomplish this by using cURL. I already have a couple of POST requests running and they all work as needed, but as soon as I try to accomplish this with a file I am running into issues.

When I try to send a file from Javascript to my Django Server with Multipart and FormData, everything works.

I tried to use the following code in PHP:

public function httpPost($url, $data, $multipart) {
        $curl = curl_init($url);
        if ($multipart) {
            // curl_setopt($curl, CURLOPT_HTTPHEADER, array('Content-Type: multipart/form-data'));    
            // curl_setopt($curl, CURLOPT_POSTFIELDS, $data);
            curl_setopt($curl, CURLOPT_POSTFIELDS, http_build_query($data));
            // curl_setopt($curl, CURLOPT_INFILE, $file_handle);
        } else {
            curl_setopt($curl, CURLOPT_POSTFIELDS, http_build_query($data));
        }
        curl_setopt($curl, CURLOPT_POST, true);
        curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
        $response = curl_exec($curl);
        if ($response === false) {
            var_dump(curl_error($curl));
        }
        curl_close($curl);
}

As you can see from the above code-snippet, I am trying to set the Header to Multipart and set the data accordingly.

I tried the following things already:

• load the file into PHP with fopen/fread then set it in the $data array. Then the file also appears kind of on the Django Server, but in the request.POST vars and not in the request.FILES vars.
• load the file into a CurlFile. Then only the file path appears on the Django Server

Always when I set multipart, the Django server can't parse the request.BODY.

Can anybody help here?