Docker Compose: WordPress + MySQL Using Shared Environment Variables

Create a project folder:

mkdir wordpress-env-demo
cd wordpress-env-demo

Create a .env file:

MYSQL_DATABASE=wordpressdb
MYSQL_USER=wpuser
MYSQL_PASSWORD=wppassword123
MYSQL_ROOT_PASSWORD=rootpassword123

WORDPRESS_PORT=8080

Create docker-compose.yml:

services:
  db:
    image: mysql:latest
    container_name: wordpress_mysql
    restart: always
    environment:
      MYSQL_DATABASE: ${MYSQL_DATABASE}
      MYSQL_USER: ${MYSQL_USER}
      MYSQL_PASSWORD: ${MYSQL_PASSWORD}
      MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
    volumes:
      - mysql_data:/var/lib/mysql

  wordpress:
    image: wordpress:latest
    container_name: wordpress_app
    restart: always
    depends_on:
      - db
    ports:
      - "${WORDPRESS_PORT}:80"
    environment:
      WORDPRESS_DB_HOST: db:3306
      WORDPRESS_DB_NAME: ${MYSQL_DATABASE}
      WORDPRESS_DB_USER: ${MYSQL_USER}
      WORDPRESS_DB_PASSWORD: ${MYSQL_PASSWORD}
    volumes:
      - wordpress_data:/var/www/html

volumes:
  mysql_data:
  wordpress_data:
Code language: JavaScript (javascript)

Start the containers:

docker compose up -d

Open WordPress:

http://localhost:8080
Code language: JavaScript (javascript)

Now students can see how environment variables are passed into both containers.

Check MySQL container env:

docker compose exec db printenv MYSQL_DATABASE
docker compose exec db printenv MYSQL_USER
docker compose exec db printenv MYSQL_PASSWORD

Check WordPress container env:

docker compose exec wordpress printenv WORDPRESS_DB_HOST
docker compose exec wordpress printenv WORDPRESS_DB_NAME
docker compose exec wordpress printenv WORDPRESS_DB_USER
docker compose exec wordpress printenv WORDPRESS_DB_PASSWORD

Verify both containers are using the same password:

docker compose exec db printenv MYSQL_PASSWORD
docker compose exec wordpress printenv WORDPRESS_DB_PASSWORD

Check how WordPress reads env and creates database config:

docker compose exec wordpress bash -lc 'grep DB_ /var/www/html/wp-config.php'
Code language: JavaScript (javascript)

Test MySQL login using the env variable inside DB container:

docker compose exec db bash -lc 'mysql -u$MYSQL_USER -p$MYSQL_PASSWORD $MYSQL_DATABASE -e "SHOW TABLES;"'
Code language: JavaScript (javascript)

Check service-name networking between containers:

docker compose exec wordpress bash -lc 'getent hosts db'
Code language: JavaScript (javascript)

This works because Docker Compose creates an internal network where db becomes the hostname of the MySQL container.

Stop everything:

docker compose down

Stop and delete volumes also:

docker compose down -v

For teaching, this is perfect. For production, avoid latest, use fixed versions like wordpress:6.8-apache and mysql:8.4, and never commit real passwords into Git.

Rajesh Kumar

I’m a DevOps/SRE/DevSecOps/Cloud Expert passionate about sharing knowledge and experiences. I have worked at Cotocus. I share tech blog at DevOps School, travel stories at Holiday Landmark, stock market tips at Stocks Mantra, health and fitness guidance at My Medic Plus, product reviews at TrueReviewNow , and SEO strategies at Wizbrand.

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