Wordpress + PhpMyAdmin + External volume

docker-compose.yml

wordpress:
  image: wordpress
  links:
    - wordpress_db:mysql
  ports:
    - 8080:80
  volumes:
    - ./html:/var/www/html
wordpress_db:
  image: mariadb
  environment:
    MYSQL_ROOT_PASSWORD: root
phpmyadmin:
  image: phpmyadmin/phpmyadmin
  links:
    - wordpress_db:mysql
  ports:
    - 8181:80
  environment:
    PMA_HOST: mysql
    PMA_PORT: 3306