Hello. I've used code below to send XML to my REST API. $xml_string_data contains proper XML, and it is passed well to mypi.php:

    //set POST variables
    $url = 'http://www.server.cu/mypi.php'; 
    $fields = array(
                'data'=>urlencode($xml_string_data)
            );

    //url-ify the data for the POST
    $fields_string = "";
    foreach($fields as $key=>$value) 
    { 
      $fields_string .= $key.'='.$value.'&'; 
    }
    rtrim($fields_string,'&');

    echo $fields_string;

    //open connection
    $ch = curl_init();

    curl_setopt($ch,CURLOPT_URL,$url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch,CURLOPT_POST,count($fields));
    curl_setopt($ch,CURLOPT_POSTFIELDS,$fields_string);
    curl_setopt($ch,CURLOPT_HTTPHEADER,array (
        "Expect: "
    ));

    //execute post
    $result = @curl_exec($ch);

But when I've added other field:

    $fields = array(
      'method' => "methodGoPay",
      'data'=>urlencode($xml_string_data)
    );

It stopped to work. On the mypi.php I don't recieve any more POST parameters at all!

Could you you please tell me what to do to send XML and other post parameters in one cURL request?

Please don't suggest using any libraries, I wan't to acomplish it in plain PHP.