Что может быть причиной этой ошибки в JSON?

Я внедряю базовую систему регистрации в приложении Android, которая подключена к SQL DATABASE через wampserver и PHP API... каждый раз, когда я выполняю процесс регистрации, пользователь получает сохранение в базе данных, но когда я пытаюсь получить ответ JSON процесс, который несет зарегистрированную информацию пользователя для хранения в базе данных SQLite, связанной с моим приложением... Я получаю сообщение об ошибке: string не может быть преобразован в объект json.

Это конец андроида, где я вызываю PHP-код для выполнения регистрации и получения ответа json.

private void registerUser(final String name, final String email,
        final String password, final String latitude,
        final String longitude, final String userType) {
    // Tag used to cancel the request
    String tag_string_req = "req_register";

    pDialog.setMessage("Registering ...");
    showDialog();

    StringRequest strReq = new StringRequest(Method.POST,
            AppConfig.URL_REGISTER, new Response.Listener<String>() {

                @Override
                public void onResponse(String response) {
                    hideDialog();

                    try {
                        Log.i("tagconvertstr", "[" + response.toString()
                                + "]");


                        JSONObject jObj = new JSONObject(response);
                        boolean error = jObj.getBoolean("error");
                        if (!error) {
                            // User successfully stored in MySQL
                            // Now store the user in sqlite
                            String uid = jObj.getString("uid");

                            JSONObject user = jObj.getJSONObject("user");
                            String name = user.getString("name");
                            String email = user.getString("email");
                            String latitude = user.getString("latitude");
                            String longitude = user.getString("longitude");
                            String userType = user.getString("userType");
                            String service = user.getString("service");
                            String rate = user.getString("rate");
                            String rated_clients = user
                                    .getString("rated_clients");
                            String servicesTag = user
                                    .getString("servicesTag");
                            String created_at = user
                                    .getString("created_at");

                            // Inserting row in users table
                            db.addUser(name, email, latitude, longitude,
                                    userType, service, rate, rated_clients,
                                    servicesTag, uid, created_at);

                            Toast.makeText(
                                    getApplicationContext(),
                                    "User successfully registered. Try login now!",
                                    Toast.LENGTH_LONG).show();

                            // Launch login activity
                            checkLogin(email, password);

                        } else {
                            Log.d("heeeeeeeeeeeeeeeey", "error here");

                            // Error occurred in registration. Get the error
                            // message
                            String errorMsg = jObj.getString("error_msg");
                            toast.makeDialog("Error in registering "
                                    + errorMsg + "kk",
                                    getApplicationContext());
                        }
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }

                }
            }, new Response.ErrorListener() {

                @Override
                public void onErrorResponse(VolleyError error) {
                    loginLayout.setVisibility(View.GONE);
                    registerLayout.setVisibility(View.GONE);
                    noConnectionLayout.setVisibility(View.VISIBLE);
                    tag = "register";
                    hideDialog();
                }
            }) {

        @Override
        protected Map<String, String> getParams() {
            // Posting params to register url
            Map<String, String> params = new HashMap<String, String>();
            params.put("name", name);
            params.put("email", email);
            params.put("password", password);
            params.put("latitude", latitude);
            params.put("longitude", longitude);
            params.put("userType", userType);

            return params;
        }

    };
    strReq.setRetryPolicy(new DefaultRetryPolicy(0,
            DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
            DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));

    // Adding request to request queue
    AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
}

Я получаю ошибку на строке: JSONObject jObj = новый JSONObject (ответ);

это код PHP для процесса регистрации:

<?php

ini_set ( 'display_errors', 'On' );

require_once 'include/DB_Functions.php';

$db = new DB_Functions ();

// json response array

$response = array (
"error" => FALSE 

');

if (isset ( $_POST ['name'] ) && isset ( $_POST ['email'] ) && isset ( $_POST ['password'] ) && isset ( $_POST ['latitude'] ) && isset ( $_POST ['longitude'] ) && isset ( $_POST ['userType'] )) {



// receiving the post params
$name = $_POST ['name'];
$email = $_POST ['email'];
$password = $_POST ['password'];
$latitude = $_POST ['latitude'];
$longitude = $_POST ['longitude'];
$userType = $_POST ['userType'];

// check if user is already existed with the same email
if ($db->isUserExisted ( $email )) {
    // user already existed
    $response ["error"] = TRUE;
    $response ["error_msg"] = "User already existed with " . $email;
    echo json_encode ( $response );
} else {
    // create a new user
    $user = $db->storeUser ( $name, $email, $password, $latitude, $longitude, $userType );

    if ($user) {
        // user stored successfully
        $response ["error"] = FALSE;
        $response ["uid"] = $user ["unique_id"];
        $response ["user"] ["name"] = $user ["name"];
        $response ["user"] ["email"] = $user ["email"];
        $response ["user"] ["latitude"] = $user ["latitude"];
        $response ["user"] ["longitude"] = $user ["longitude"];
        $response ["user"] ["userType"] = $user ["userType"];
        $response ["user"] ["service"] = $user ["service"];
        $response ["user"] ["rate"] = $user ["rate"];
        $response ["user"] ["rated_clients"] = $user ["rated_clients"];
        $response ["user"] ["servicesTag"] = $user ["servicesTag"];
        $response ["user"] ["created_at"] = $user ["created_at"];
        $response ["user"] ["updated_at"] = $user ["updated_at"];
        echo json_encode ( $response );
    } else {

        // user failed to store
        $response ["error"] = TRUE;
        $response ["error_msg"] = "Unknown error occurred in registration!";
        echo json_encode ( $response );
    }
}
} else {
$response ["error"] = TRUE;
$response ["error_msg"] = "Required parameters (name, email or password) is missing!";
echo json_encode ( $response );
}
?>

Это функции isUserExicted и storeUser:

public function isUserExisted($email) {
    $stmt = $this->conn->prepare ( "SELECT email from users WHERE email = ?" );

    $stmt->bind_param ( "s", $email );

    $stmt->execute ();

    $stmt->store_result ();

    if ($stmt->num_rows > 0) {
        // user existed
        $stmt->close ();
        return true;
    } else {
        // user not existed
        $stmt->close ();
        return false;
    }
}


public function storeUser($name, $email, $password, $latitude, $longitude, $userType) {
    $uuid = uniqid ( '', true );
    $hash = $this->hashSSHA ( $password );
    $encrypted_password = $hash ["encrypted"]; // encrypted password
    $salt = $hash ["salt"]; // salt

    $service = "none";
    $rate = "none";
    $rated_clients = "none";
    $servicesTag = "none";

    $stmt = $this->conn->prepare ( "INSERT INTO users(unique_id, name, email, encrypted_password, latitude, longitude, userType, salt, service, rate, rated_clients, servicesTag, created_at) VALUES(?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, NOW())" );
    $stmt->bind_param ( "ssssssssssss", $uuid, $name, $email, $encrypted_password, $latitude, $longitude, $userType, $salt, $service, $rate, $rated_clients, $servicesTag );
    $result = $stmt->execute ();
    $stmt->close ();
    var_dump ( $result );
    // check for successful store
    if ($result) {

        $stmt = $this->conn->prepare ( "SELECT * FROM users WHERE email = ?" );

        $stmt->bind_param ( "s", $email );

        $stmt->execute ();
        $user = $stmt->get_result ()->fetch_assoc ();
        $stmt->close ();
        var_dump ( $user );
        echo '</pre>';

        return $user;
    } else {

        return null;
    }
}

это значение ответа:

Примечание: столбцы, привязанные к запросу в методе storeUser, гарантированно создаются в базе данных.