'user_key' => urlencode($fields['user_key']), // May be null.
'file_name' => urlencode($fields['file_name']),
'description' => urlencode($fields['description']),
'user_key' => urlencode($fields['user_key']), // May be null.
'file_name' => urlencode($fields['file_name']),
'description' => urlencode($fields['description']),