Docker-compose.yml reverse proxy (NGINX) and https' encryption (Lest's encrypt) :

version: '3'

services:
  nginx:
    image: nginx:1.13.1
    container_name: nginx-proxy
    ports:
      - "80:80"
      - "443:443"
    expose:
      - "80"
      - "443"
    volumes:
      - ./conf.d:/etc/nginx/conf.d
      - ./vhost.d:/etc/nginx/vhost.d
      - ./html:/usr/share/nginx/html
      - certs:/etc/nginx/certs
    labels:
      - "com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy=true"

  dockergen:
    image: jwilder/docker-gen:0.7.3
    container_name: nginx-proxy-gen
    depends_on:
      - nginx
    command: -notify-sighup nginx-proxy -watch -wait 5s:30s /etc/docker-gen/templates/nginx.tmpl /etc/nginx/conf.d/default.conf
    volumes:
      - ./conf.d:/etc/nginx/conf.d
      - ./vhost.d:/etc/nginx/vhost.d
      - ./html:/usr/share/nginx/html
      - certs:/etc/nginx/certs
      - /var/run/docker.sock:/tmp/docker.sock:ro
      - ./nginx.tmpl:/etc/docker-gen/templates/nginx.tmpl:ro

  letsencrypt:
    image: jrcs/letsencrypt-nginx-proxy-companion
    container_name: nginx-proxy-le
    depends_on:
      - nginx
      - dockergen
    environment:
      NGINX_PROXY_CONTAINER: nginx-proxy
      NGINX_DOCKER_GEN_CONTAINER: nginx-proxy-gen
    volumes:
      - ./conf.d:/etc/nginx/conf.d
      - ./vhost.d:/etc/nginx/vhost.d
      - ./html:/usr/share/nginx/html
      - certs:/etc/nginx/certs
      - /var/run/docker.sock:/var/run/docker.sock:ro

volumes:
  conf:
  vhost:
  html:
  certs:

# Do not forget to run the command 'docker network create nginx-proxy' before launch, and to add '--network nginx-proxy' to proxied containers so the reverse proxy and encryption work.

networks:
  default:
    external:
      name: nginx-proxy




docker-compose.yml wordpress website 1 :
version: "3"

services:
  db_site1:
    image: mysql:5.7
    volumes:
       - ./db_data:/var/lib/mysql
#    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: ROOT_PASSWORD1
      MYSQL_DATABASE: wordpress
      MYSQL_USER: wordpress
      MYSQL_PASSWORD: PASSWORD1
    container_name: db_wp_site1

  wordpress:
    depends_on:
      - db_site1
    image: wordpress:latest
    volumes:
      - ./wordpress:/var/www/html
#    restart: always
    environment:
      VIRTUAL_HOST: domain1.com, www.domain1.com
      LETSENCRYPT_HOST: domain1.com, www.domain1.com
      LETSENCRYPT_EMAIL: EMAIL
      WORDPRESS_DB_HOST: db_site1:3306
      WORDPRESS_DB_USER: wordpress
      WORDPRESS_DB_PASSWORD: PASSWORD
    container_name: wp_site1

volumes:
  db_data:

networks:
  default:
    external:
      name: nginx-proxy

docker-compose.yml wordpress website 2 :
version: "3"

services:
  db_site2:
    image: mysql:5.7
    volumes:
       - ./db_data:/var/lib/mysql
#    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: ROOT_PASSWORD2
      MYSQL_DATABASE: wordpress
      MYSQL_USER: wordpress
      MYSQL_PASSWORD: PASSWORD2
    container_name: db_wp_site2

  wordpress:
    depends_on:
      - db_site2
    image: wordpress:latest
    volumes:
      - ./wordpress:/var/www/html
#    restart: always
    environment:
      VIRTUAL_HOST: domain2.com, www.domain2.com
      LETSENCRYPT_HOST: domain2.com, www.domain2.com
      LETSENCRYPT_EMAIL: EMAIL
      WORDPRESS_DB_HOST: db_site2:3306
      WORDPRESS_DB_USER: wordpress
      WORDPRESS_DB_PASSWORD: PASSWORD2
    container_name: wp_site2

volumes:
  db_data:

networks:
  default:
    external:
      name: nginx-proxy


docker-compose.yml wordpress website 3 :
version: "3"

services:
  db_site3:
    image: mysql:5.7
    volumes:
       - ./db_data:/var/lib/mysql
#    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: ROOT_PASSWORD3
      MYSQL_DATABASE: wordpress
      MYSQL_USER: wordpress
      MYSQL_PASSWORD: PASSWORD3
    container_name: db_wp_site3

  wordpress:
    depends_on:
      - db_site3
    image: wordpress:latest
    volumes:
      - ./wordpress:/var/www/html
#    restart: always
    environment:
      VIRTUAL_HOST: domain3.com, www.domain3.com
      LETSENCRYPT_HOST: domain3.com, www.domain3.com
      LETSENCRYPT_EMAIL: EMAIL
      WORDPRESS_DB_HOST: db_site3:3306
      WORDPRESS_DB_USER: wordpress
      WORDPRESS_DB_PASSWORD: PASSWORD3
    container_name: wp_site3

volumes:
  db_data:

networks:
  default:
    external:
      name: nginx-proxy