Install the gRPC PHP plugin

install-grpc-php-on-mac.sh

# Install the gRPC PHP plugin on Mac
#
# See: http://www.grpc.io/docs/quickstart/php.html#install-protobuf-plugin
# Source: https://gist.github.com/johndpope/503029706ed56d5375d1e9469f0135d4

# Install build dependencies
brew install automake libtool

## Clone gRPC repo
git clone --recursive -b v1.4.x https://github.com/grpc/grpc
cd grpc

cd third_party/protobuf 
./autogen.sh
./configure CC=clang CXX=clang++
make
make install

cd ../..

make 
make grpc_php_plugin

Mac OS 10.15, Not working with me, have error
./configure CC=clang CXX=clang++
Change:
./configure AR=/usr/bin/ar RANLIB=/usr/bin/ranlib

This should be faster

git clone --recursive --depth 1 --shallow-submodules -b ...

A note for people who just use brew... do:

brew install grpc

As of 13th Oct 2021 you only get version 1.39.1 but will still provide grpc_php_plugin in /usr/local/bin/grpc_php_plugin

Thank you very much @peterfox this is definitely the best option. It was installed in the folder /opt/homebrew/Cellar/grpc/1.60.0_1/bin/grpc_php_plugin for me (which is the new folder homebrew install stuff iirc).