The API is pretty straightforward. There were no PHP samples but the docs are fine. We discovered a couple of things regarding VAT that weren’t clear but the support team at Xero helped us out quickly.

One thing to be aware of in the UK is that as Xero are based in New Zealand we were having to wait overnight sometimes to get answers, but as long as you aren’t trying to do things in a crazy rush that isn’t a problem.

They have a sandbox for testing and once you are ready to go you have to have your usage of the API verified by Xero. They wanted to see 20 or so correct transactions before they would verify us and allow us to use the live server. This was helpful though as it meant we were sure everything was being created correctly and I’ve not had any problems with the data that is coming into our live account now we are live with the API.