phpinfo() shows all the information about your PHP runtime, including the extension options and versions.
Now grpc extension only reports that it's enabled. I think it should report its version too.

FYI @chingor13 added it for the opencensus extension
https://github.com/census-instrumentation/opencensus-php/pull/42/files