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'); }