Http request using get variables

I have a database with username ,password and email.
When a new customer click the submit button these details must be sent to a third party server.
This server has built API requests like above : https://thirdpartyserver.com/API/Request.ashx?command=createcustomer&username=_&password=_&customer=_&customerpassword=_

Can someone help me writing the code for this procedure?