protobuf php extension does not provide a config.w32
I'm not sure if it's a feature or a bug, but no attempt is made to build the php extension for Windows because it does not provide a config.w32
This extension is supposed (by Google documentation) to be available as a DLL file:
https://cloud.google.com/php/grpc#installing_the_protobuf_runtime_library

Could you please add this config file?
This is a good request, but unfortunately not a top priority for our team. We would love to accept a PR for this.
I am pleased to announce that this extension is now compiled for Windows by the PHP Extension Repository site.
You can download the DLLs on the extension page: https://phpext.phptools.online/extension/tools-and-utilities/protobuf-292
If you have any questions, I am available to discuss them.