Connect QuickBooks Online to our custom PHP website

We are looking for a quickbooks developer to create an app or connection to sync/push invoices from our custom PHP website to "QuickBooks Online" accounting software. There is an existing solution where an app can be created (API) on the Intuit Developer website which can be utilized. Other suggestions are welcome!

Please let us know if you have experience with this type of coding and approximate cost.

Thank you!