function DigitalUsecase()
{
    echo "<h2>Server 2 Server Checkout Request</h2>";
    $merchant_id = "";
    // Your Merchant ID
    $merchant_key = "";
    // Your Merchant Key
    $server_type = "sandbox";
    $currency = "USD";
    $cart = new GoogleCart($merchant_id, $merchant_key, $server_type, $currency);
    echo $cart->CheckoutServer2ServerButton('digitalCart.php');
}