title: MongoClient php class does not exist
body: <p>I'm using docker to run my website.
  I built php-fpm container for php using.</p>
  
  <p>Phpinfo shows this info in the browser:</p>
  
  <pre><code>Additional .ini files parsed    
  /usr/local/etc/php/conf.d/docker-php-ext-gd.ini, 
  /usr/local/etc/php/conf.d/docker-php-ext-mcrypt.ini, 
  /usr/local/etc/php/conf.d/docker-php-ext-mongodb.ini, 
  /usr/local/etc/php/conf.d/docker-php-ext-mysqli.ini, 
  /usr/local/etc/php/conf.d/docker-php-ext-pdo_mysql.ini, 
  /usr/local/etc/php/conf.d/docker-php-ext-soap.ini, 
  /usr/local/etc/php/conf.d/docker-php-ext-zip.ini, 
  /usr/local/etc/php/conf.d/ext-xdebug.ini
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/AnHVO.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/AnHVO.jpg" alt="enter image description here"></a></p>
  
  <p>But at the same time class_exists('MongoClient') returns <code>false</code></p>
  
  <p>My docker-compose.yml (that is not all services):</p>
  
  <pre><code>installer:
    image: andreaskoch/dockerized-magento-installer
    environment:
      DOMAIN: dockerized-magento.local
    volumes_from:
      - nginx
    volumes:
      - ./config/installer/bin/install.sh:/bin/install.sh
    links:
      - "cache:rediscache"
      - "sessions:redissession"
      - "fullpagecache:redisfullpagecache"
      - "solr:solr"
      - "mysql:mysql"
      - "mongodb:mongodb"
    entrypoint: /bin/install.sh
  nginx:
    image: nginx:latest
    ports:
      - "80:80"
      - "443:443"
    links:
      - "php"
    volumes:
      - ./logs/nginx:/var/log/nginx
    volumes_from:
      - php
  php:
    image: avestique/php7_fpm
    links:
      - "cache:rediscache"
      - "sessions:redissession"
      - "fullpagecache:redisfullpagecache"
      - "solr:solr"
      - "mysql:mysql"
      - "mongodb:mongodb"
    volumes:
      - ./config/installer/php/php.ini:/usr/local/etc/php/php.ini
      - ./config/installer/php/ext-xdebug.ini:/usr/local/etc/php/conf.d/ext-xdebug.ini
      - ./htdocs:/var/www/htdocs
  mongodb:
    image: mongo:latest
    environment:
      - MONGO_DATA_DIR=/data/db
      - MONGO_LOG_DIR=/dev/null
    volumes:
      - ./data/mongo:/data/db
    ports:
        - 27017:27017
    command: mongod --smallfiles --logpath=/dev/null
  </code></pre>
  
  <p>Actually andreaskoch/dockerized-magento-installer has php5.6. But again - phpinfo shows <code>PHP Version 7.0.28</code> and <code>Server API FPM/FastCGI</code> and it looks to 
  avestique/php7_fpm image. </p>
  
  <p><strong>Why MongoClient is not shown then?</strong></p>