During my career as a Software Engineer at Sylius, we were working on a Multi-Vendor Marketplace platform. The platform was supposed to be built on top of Sylius but the core of our new product was going to written using new techniques and technologies. One of them was GraphQL. We decided that for Vendors Backend, we will go headless for sure. Instead of going with a standard approach like REST API, we decided that Facebook's concept of building more flexible APIs using GraphQL suits us more at that time.
On March 28th, 2018, I made a presentation on local PHPers Meetup. During my talk, I spoke about the libraries and challenges that we faced during the development of such an API in PHP.
If you are curious, the slides from this event are available here: