php stellar-sdk memo

<?php

require '../vendor/autoload.php';

use \ZuluCrypto\StellarSdk\Keypair;
use \ZuluCrypto\StellarSdk\Server;
use \ZuluCrypto\StellarSdk\XdrModel\Memo;

$server = Server::testNet();
$sourceKeypair = Keypair::newFromSeed('SDAP46Z3PXPZLZELRBLRCMS72C23LHHDCGJ2U3D6K5DXUN6A4KARNUNT');


$response = $server->buildTransaction($sourceKeypair)
    ->addLumenPayment('GC523S5PPKDICBH3UPLPYJYVQY2U4N6O73EYJHE4OE35PGR3EQEQ3OHS', 1)
    ->setMemo( new Memo(Memo::MEMO_TYPE_TEXT, "Hello World"))
    ->submit($sourceKeypair);

$result = $response->getResult();
echo $result->getResultCode();