authorize.net Gateway Response

I need to store response from [login to view URL] payment gateway into mysql based on submission. I just need to store information based on user id and update a field in mysql. This should not be complicated. No design required. All scripts already available. I really just need the php coding for parsing response from [login to view URL] (SIM) and store the response in a table and update a field in mysql. I need this ASAP. I pay right away. Let me know if you had experience integrating [login to view URL]