org.json.JSONException: Value <br of type java.lang.String cannot be converted to JSONObject

require_once 'include/DB_Functions.php';
$db = new DB_Functions();

// json response array
$response = array("error" => FALSE);

if (isset($_POST['email']) && isset($_POST['password'])) {

    // receiving the post params
    $email = $_POST['email'];
    $password = $_POST['password'];

    // get the user by email and password
    $user = $db->getUserByEmailAndPassword($email, $password);

    if ($user != false) {
        // use is found
        $response["error"] = FALSE;
        $response["uid"] = $user["unique_id"];
        $response["user"]["name"] = $user["name"];
        $response["user"]["cognome"] = $user["cognome"];
        $response["user"]["email"] = $user["email"];
        $response["user"]["email2"] = $user["email2"];
        $response["user"]["numero_appartamento"] = $user["numero_appartamento"];
        $response["user"]["nome_edificio"] = $user["nome_edificio"];
        $response["user"]["zona_metropolitana"] = $user["zona_metropolitana"];
        $response["user"]["created_at"] = $user["created_at"];
        $response["user"]["updated_at"] = $user["updated_at"];
        echo json_encode($response);
    } else {
        // user is not found with the credentials
        $response["error"] = TRUE;
        $response["error_msg"] = "Login credentials are wrong. Please try again!";
        echo json_encode($response);
    }
} else {
    // required post params is missing
    $response["error"] = TRUE;
    $response["error_msg"] = "Required parameters email or password is missing!";
    echo json_encode($response);
}
?>

private void checkLogin(final String email, final String password) {
        // Tag used to cancel the request
        String tag_string_req = "req_login";

        pDialog.setMessage("Logging in ...");
        showDialog();

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

            @Override
            public void onResponse(String response) {
                Log.d(TAG, "Login Response: " + response.toString());
                hideDialog();

                try {
                    JSONObject jObj = new JSONObject(response);
                    boolean error = jObj.getBoolean("error");

                    // Check for error node in json
                    if (!error) {
                        // user successfully logged in
                        // Create login session
                        session.setLogin(true);

                        // Now store the user in SQLite
                        String uid = jObj.getString("uid");

                        JSONObject user = jObj.getJSONObject("user");
                        String name = user.getString("name");
                        String cognome = user.getString("cognome");

                        String email = user.getString("email");
                        String email2 = user.getString("email2");
                        String numero_appartamento = user.getString("numero_appartamento");
                        String nome_edificio = user.getString("nome_edificio");
                        String zona_metropolitana = user.getString("zona_metropolitana");



                        String created_at = user
                                .getString("created_at");

                        // Inserting row in users table
                        db.addUser(name,cognome, email,email2,numero_appartamento,nome_edificio,zona_metropolitana,uid, created_at);

                        // Launch main activity
                        Intent intent = new Intent(LoginActivity.this,
//                                MainActivity.class);
                                ScrollableTabsActivity.class);

                        startActivity(intent);
                        finish();
                    } else {
                        // Error in login. Get the error message
                        String errorMsg = jObj.getString("error_msg");
                        Toast.makeText(getApplicationContext(),
                                errorMsg, Toast.LENGTH_LONG).show();
                    }
                } catch (JSONException e) {
                    // JSON error
                    e.printStackTrace();
                    Toast.makeText(getApplicationContext(), "Json error: " + e.getMessage(), Toast.LENGTH_LONG).show();
                }

            }
        }, new Response.ErrorListener() {

            @Override
            public void onErrorResponse(VolleyError error) {
                Log.e(TAG, "Login Error: " + error.getMessage());
                Toast.makeText(getApplicationContext(),
                        error.getMessage(), Toast.LENGTH_LONG).show();
                hideDialog();
            }
        }) {

            @Override
            protected Map<String, String> getParams() {
                // Posting parameters to login url
                Map<String, String> params = new HashMap<String, String>();
                params.put("email", email);
                params.put("password", password);
                System.out.println(params);
                return params;
            }

        };

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

JSONObject jObj = new JSONObject(response);

AppConfig.URL_LOGIN, new Response.Listener<String>()