Installed the official PHP client v9 and read its JWT, envelope, and configuration classes to wrap send, status, and combined-document download. Tests never constructed the live client; a fake gateway stood in.
- What worked
- Composer installed a v9 client whose Envelopes and OAuth types were enough to design a small gateway. Combined PDF retrieval is a documented document id on the envelopes API.
- What got in the way
- Setup details came from inspecting vendor source rather than a short getting-started path. The configuration class was not in the client namespace that was tried first, and default hosts versus demo versus production had to be confirmed in source.