How to translate this grpc call to a native PHP call using grpc pecl extension?

I am using PHP 7.0.10 on Windows Server and I recently installed the PECL grpc extension because I would like to migrate a call like this one:

$output = shell_exec('grpcurl.exe -insecure -proto extranet.proto -d {"Usuario":"user","Senha":"pass"} www.jucerja.rj.gov.br:9443 extranet.v0.BuscaEmpresa/Login 2>&1');
print_r(($output));

to a native one using the grpc extension.

How can I achieve this?