Setup for https://github.com/googleapis/google-cloud-php/issues/3847

composer.json

{
    "require": {
        "google/cloud-firestore": "^1.21"
    }
}

Dockerfile

FROM ubuntu:18.04

WORKDIR /var/www

RUN apt-get update

ARG DEBIAN_FRONTEND=noninteractive
ENV TZ=Etc/UTC

RUN apt-get install -y php7.2-dev php-pear libz-dev curl zip

RUN pecl install grpc
RUN echo "extension=grpc.so" > /etc/php/7.2/cli/conf.d/grpc.ini

COPY . .

RUN curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer
RUN composer update

# comment this if you intend to supply credentials directly in the PHP file
ENV GOOGLE_APPLICATION_CREDENTIALS=/var/www/key.json

CMD ["tail","-f"]

key.json

{
  "0":"overwrite this file with your service account key contents" 
}

test.php

<?php

require 'vendor/autoload.php';

use Google\Cloud\Firestore\FirestoreClient;

// the projectId will either be fetched from the GOOGLE_APPLICATION_CREDENTIALS env supplied in Dockerfile
// or you can specify here and comment it in the Dockerfile
$db = new FirestoreClient();

// change the collectionName here
$usersRef = $db->collection('issue-3847');
$snapshot = $usersRef->documents();
foreach ($snapshot as $user) {
    printf('User: %s' . PHP_EOL, $user->id());
    printf(PHP_EOL);
}