Can't get access to DB via phpmyadmin - docker

[admin]

I'm pretty new to docker and I guess I have made a proper beginner mistake here but I really can't get my head around of what's wrong...

I have sucesfully created a docker container with a running Wordpress installation. The link to the DB does work there. I can also access phpmyadmin but I can't get in. The following errors appear:

<ul>
<li>Invalid hostname for server 1. Please review your configuration.</li>
<li>Connection for controluser as defined in your configuration failed.</li>
</ul>

This is my

docker.yml

version: "2"
services:
  my-wpdb:
    image: mariadb
    environment:
      MYSQL_ROOT_PASSWORD: letmein
  my-wp:
    image: wordpress
    volumes:
      - ./:/var/www/html
    ports:
      - "8080:80"
    links:
      - my-wpdb:mysql
    environment:
      WORDPRESS_DB_PASSWORD: letmein
  phpmyadmin:
    image: corbinu/docker-phpmyadmin
    links:
        - my-wpdb:mysql
    ports:
        - 8181:80
    environment:
        MYSQL_USERNAME: letmein
        MYSQL_ROOT_PASSWORD: letmein

I'm trying to log in with: <strong>root, letmein</strong>

Thank's! Any help appeciated!