Why can't I seem to upload a document to a project? Help please!

Posted on behalf of Daniel. Original posting date 2014-08-29.

Here is an excerpt of my code, for some reason it is not working, I get no response...

$files = array( 
"document[file_name]" => "REF_test.jpg", 
"document[attached_file]" => "@http://staff:8888/wp-content/uploads/gravity_forms/1-3bab614b6c004fcb7b90a7b24fea4764/2014/08/test.jpg", 
);

curl_setopt($conn, CURLOPT_URL, $url."/projects/".$projectID."/documents" ); 
curl_setopt($conn, CURLOPT_POST, true); 
curl_setopt($conn, CURLOPT_POSTFIELDS, $files);

$responseDocument = json_decode(curl_exec($conn));

I know the project ID works because I am attaching a Note tot he project just fine. Do you see anythign that should make this not work?