For german users a similar service is offered by 1&1 (iPayment, with "silent CGI"-mode). The form on the site is sent to the ipayement servers and those verify

For german users a similar service is offered by 1&1 (iPayment, with "silent CGI"-mode). The form on the site is sent to the ipayement servers and those verify the transaction data, call a URL on your servers with the unique transaction token and success/error message, and only redirect the user back to your site after the callback is finished. Works pretty well, the credit card data never touches your server but the user doesn't notice that he left your site.