$ cat docker-compose.yml
version: '3'
services:
  db:
    image: mysql
    environment:
      MYSQL_ROOT_PASSWORD: password
    ports:
      # just if you also want to access it directly from you host
      # node neede for phpmyadmin
      - "3306:3306"
  phpmyadmin:
    image: phpmyadmin/phpmyadmin
    depends_on:
      - db
    ports:
      - "8080:8080"