QuickBooks PHP Integration

I have a Drupal 7 website that we take bookings on. Each booking is a php object with an associative array of fields. I want to create a script that will "sync" the booking on the website, with invoices in a QuickBooks online account.

So far I have a working module that allows a user to connect to their Quickbooks account, this returns an auth token, and I save this on the website. I am using the PHP SDK library at https://github.com/intuit/QuickBooks-V3-PHP-SDK

I am more than capable of arranging the data into the correct format in order to push the data through to Quickbooks. However I am stuck on the part where the SDK is used to create/update/delete data. No matter what I try I am getting 401 bad request, or not authenticated errors, and I am running out of time / patience.

What i need from YOU is.....

1. A function to POST (create) a customer and then a function to POST (create) a booking / invoice for that customer in QuickBooks.
3. A function to PUT (update) an invoice in QuickBooks.
4. A function to delete a booking/invoice from QuickBooks.

I will provide....

- My module in its current state
- Explanation of what ive done so far if needed