Payment gateway redirection from callback url

[subham93]

I have developed a new payment gateway plugin and after getting redirected to whmcs/modules/gateways/callback/my_gateway.php I have checked status response did:

 

addInvoicePayment($invoiceid,$transid,$amount,$gatewaymodule);

logTransaction($GATEWAY["name"],$_REQUEST,"Successful");

 

After this I get a blank page showing my callback url. Instead I need to show order-completed state. How can I reach that.