Wordpress 3.9.1 docker compose with mysql

docker-compose.yml

db:
  image: mysql:5.7
  restart: always
  ports:
    - 3306:3306
  volumes:
    - db_data:/var/lib/mysql
  environment:
    MYSQL_ROOT_PASSWORD: secret

wordpress:
  links:
    - db:mysql
  image: wordpress:3.9.1
  restart: always
  volumes:
    - ./wp-content:/var/www/html/wp-content
  environment:
    WORDPRESS_DB_HOST: db
    WORDPRESS_DB_PASSWORD: secret
  ports:
    - 127.0.0.1:80:80
    - 127.0.0.1:443:443