INSERT query works in SQL but doesn't work from android app

I'm trying to send an INSERT query to my SQL DataBase but it doesn't work and no error is appearing but the query works if I send it from phpMyAdmin. here is my PHP code :

if ($_POST['func'] == 2) {
$dbca = taskdb();
$dbca->set_charset("utf8");
$mobileUser = $_POST['phone'];
$fullnameUser = $_POST['fullname'];
$usernameUser = $_POST['username'];
$sql = "INSERT INTO users (UserPhone, Username, UserFullname) VALUES (?,?,?)";
$result = $dbca->prepare($sql);
$result->bind_param("sss", $mobileUser,$fullnameUser,$usernameUser);
echo json_encode(array('profileUser' => 'DONE'));
}

and here is my java(client) code which is inside an AsyncT doInBacground:

HttpClient httpclient = new DefaultHttpClient();
  HttpPost httppost = new HttpPost("http://192.168.2.26/MyProject/fetchData.php");
  try {
    List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
    nameValuePairs.add(new BasicNameValuePair("func", "2"));
    nameValuePairs.add(new BasicNameValuePair("phone", Login.user_phone));
    nameValuePairs.add(new BasicNameValuePair("fullname", fullname.getText().toString()));
    nameValuePairs.add(new BasicNameValuePair("username", username.getText().toString()));
    Log.e("mainToPost", "mainToPost" + nameValuePairs.toString());
    UrlEncodedFormEntity form;
    form = new UrlEncodedFormEntity(nameValuePairs,"UTF-8");
    httppost.setEntity(form);
    HttpResponse response = httpclient.execute(httppost);
    InputStream inputStream = response.getEntity().getContent();
    Signup.InputStreamToStringExample str = new Signup.InputStreamToStringExample();
    responseSignup = str.getStringFromInputStream(inputStream);
    Log.e("response", "response -----" + responseSignup);
    jsonresponse = new JSONObject(responseSignup);
  } catch (Exception e) {
    e.printStackTrace();
  }
  return null;

I'm getting "DONE" as the response in client but no row would be inserted into my DataBase. any help will be much appreciated.