PHP Integration with Authorize.Net

Through my website, users will have the ability to sign up for a service and pay either monthly or annually. ? I have an account with [login to view URL] ? that includes Automated Recurring Billing and need assistance integrating my web forms with the [login to view URL] Advanced Integration Module. I need the code that will do the following: -Charge a card for one-off transactions that are not recurring -Create a new billing subscription with [login to view URL] -Modify a billing subscription with [login to view URL] -Cancel a billing subscription with [login to view URL] -Output an appropriate error if card is declined or accepted The important thing here is for good comments/notes in the code. ? I'm not a PHP expert so I'll need some help understanding how the code works and where I need to substitute variables from my forms. Thank you! Jason