How to add a basket for checks to Sberbank acquiring using regular php?

Question

PHP

Good afternoon.
Faced error #8 - [orderBundle].
Can you please tell me if I have correctly compiled an array for the basket (I send it to the online cash register in the personal account of the Savings Bank)?

$requestpay = array(
        'userName' => '***',
        'password' => '****',
        'orderNumber' =>  $order_id,
        'amount' => $sum * 100,
        'returnUrl' => $thispage,
        'failUrl' => $thispage,
        'description' => 'Заказ №' . $order_id . ' на ***.ru',
        'taxSystem' => 0,
        
      
);
 $requestpay['orderBundle']['cartItems']['items'][] = array(
  'positionId' => '1',
  'name' => 'nameStuff',
  'quantity' => array(
    'value' => 1,
    'measure' =>  'cnt'
  ),
  'itemAmount' =>$sum * 100, 
  'itemCode' =>  '123',
  'tax' => array(
    'taxType' => 0
  ),
  'itemPrice' => $sum * 100
 );

It works fine without the basket.