[Android]: How can I communicate with php server using httpUrlconnection post with data in outputStream and ensure that server gets in $_POST?

I am using HttpURLConnection to pass json query to php server and it doesn't work the way I want.

The connection is fine, I got proper error respond from server side and I am sure the json string is properly handled. eg:
{"id":55,"date":"2011111","text":"","latitude":13.0,"longitude":123.0,"share":0,"image":"Image","sound":"sound"}

However, the php server cannot load the variable $_POST with the string that I have sent. The code on android side is simple:

    String temp_p = gson.toJson(diary);
    URL url2 = new URL( "http://localhost:8080/****");
    HttpURLConnection connection = (HttpURLConnection)url2.openConnection();
    connection.setRequestMethod("POST");
    connection.setRequestProperty("Content-Type", "application/json");
    connection.setDoInput(true);
    connection.setDoOutput(true);
    connection.connect();

    //Send request
    DataOutputStream wr = new DataOutputStream(
            connection.getOutputStream ());
    wr.writeBytes(temp_p);
    wr.flush();
    wr.close();

    //Get Response
    InputStream is = connection.getInputStream();
    BufferedReader rd = new BufferedReader(new InputStreamReader(is));
    String line;
    StringBuffer response = new StringBuffer();
    while((line = rd.readLine()) != null) {
        response.append(line);
        response.append('\r');
    }
    rd.close();
    System.out.println("respons:" + response.toString());

The code on php server looks like:

if (isset($_POST['id'])) {
    $id = $_POST['id'];
    ..blablabla..
}
else {
    // required field is missing
    $response["success"] = 0;
    $response["message"] = "Required field(s) is missing"  ;
    $response["_POST"] = $_POST  ;
    echo json_encode($response);
}

The $_POST is null in this case no matter what I sent ..

And after reaserching a bit, I found a solution that I have to modify the code on server side like the following:

$json = file_get_contents('php://input');
$request = json_decode($json, true);    
if (isset($request['id'])) {
    $id = $request['id'];

Without touching the android code, the server can recieve and work on json data I sent now.

The problem is there is no way I can modify the code on the actual server.. So any idea why the $_POST not getting p