The firestore library requires GRPC and the default version included with extension=grpc.so throws an error:
PHP Fatal error: Uncaught Exception: ERROR: Creation of dynamic property Grpc\Call::$channel is deprecated on line 60 in file /workspace/vendor/grpc/grpc/src/lib/AbstractCall.php.
Did you ever find a solution to this?
Unfortunately not. I’ve pinned down the issue to being related to the PHP release of GRPC not being up to date (the latest versions have not been released).
Currently have an issue marked in the github requesting they update it: https://github.com/grpc/grpc/issues/35324