notifyUrl inside Rest Payment?

[futdev]

$gateway = Omnipay::create('PayPal_Rest');

// Initialise the gateway
$gateway->initialize([
    'clientId' => config('settings.paypal_client_id'),
    'secret'   => config('settings.paypal_client_secret'),
    'testMode' => config('settings.paypal_sandbox'),
]);

$items[] = [
    'name' => 'Item',
    'description' => 'blah blah blah',
    'price' => 5.00,
    'quantity' => '1'
];

$params = [
    'cancelUrl' => url('paypal/' . $db_item->id . '/pay/cancel'),
    'notifyUrl' => url('paypal/ipn/'.$db_item->id),
    'returnUrl' => url('paypal/' . $db_item->id . '/pay/success'),
    'currency' => Config::get('settings.currency'),
    'amount' => 5.00
];

$response = $gateway->purchase($params)->setItems($items);
$data = $response->getData();
$data['transactions'][0]['custom'] = 'custombuypay';
$response = $response->sendData($data);

if ($response->isRedirect()) {
    $response->redirect()
}

It seems to appear that my notifyUrl isn't even being added into the $response->getData when I do a var_dump is this something that isn't supported by PayPal? or is it something that isn't supported by this package?