A full configured gitlab ci config demo

.gitlab-ci.yml

stages:
  - build
  - test
  - deploy

before_script:
  - mkdir -p ~/.ssh
  - echo "$SSH_PRIVATE_KEY" | tr -d '\r'  > /root/.ssh/id_rsa
  - chmod -R 600 ~/.ssh
  - echo "$SSH_KNOWN_HOSTS" > ~/.ssh/known_hosts #make sure remote servers's ssh host keys  are verified
  - chmod 644 ~/.ssh/known_hosts
  - mkdir -p /etc/ansible
  - echo -e "xx.xx.xxx.xxx db_master\nxx.xx.xxx.xxx db_slave" >> /etc/hosts # #this let container have access to mysql server


# cache vendor packages between jobs
cache:
  key: ${CI_COMMIT_REF_SLUG}
  paths:
    - vendor/

# environment variables set for services
variables:
  MYSQL_DATABASE: project_database_name
  MYSQL_USER: homestead
  MYSQL_PASSWORD: secret
  MYSQL_ROOT_PASSWORD: secret

# the 'pages' job will deploy and build your site to the 'public' path
pages:
  stage: deploy
  script:
  - pushd wiki && gitbook build ./ ../public/wiki && popd
  - apidoc -i app/Http/Controllers/ -o public/apidoc -t apidoc/template/
  - phpcs app --report=source --standard=PSR2 >> public/phpcs_source.html || echo "success"
  - phpcs app --standard=PSR2 >> public/phpcs.html || echo "success"
  - phpcs app --report=diff --standard=PSR2 >> public/phpcs_diff.diff || echo "success"
  - diff2html -i file -d char -s side -F public/phpcs_diff.html -- public/phpcs_diff.diff || echo "success"
  - phpmd app  html codesize,unusedcode,naming >> public/phpmd_Model.html || echo "success"
  artifacts:
    paths:
      - public
  only:
    - master
    - develop
  tags:
    - your-runner-tag

build:
  stage: build
  image: kevinyan001/git-runner:php7.1-node10
  script:
    - /usr/local/bin/composer install
  only:
    - develop
    - uat
  tags:
    - your-runner-tag

test-dev:
  stage: test
  image: kevinyan001/git-runner:php7.1-node10
  variables: # set env variables, then job container can connect to the mysql service
    DB_HOST: mysql
    DB_PORT: '3306'
    DB_DATABASE: project_database_name
    DB_USERNAME: homestead
    DB_PASSWORD: secret
  services:
    - mysql:5.7
  script:
    - php artisan migrate:refresh --seed
    - ./vendor/bin/phpunit
  only:
    - develop
  tags:
    - your-runner-tag

test-uat:
  stage: test
  image: kevinyan001/git-runner:php7.1-node10
  variables: # set env variables, then job container can connect to the mysql service
    DB_HOST: mysql
    DB_PORT: '3306'
    DB_DATABASE: project_database_name
    DB_USERNAME: homestead
    DB_PASSWORD: secret
  services:
    - mysql:5.7
  script:
    - cp .env.uat .env
    - php artisan migrate:refresh --seed
    - ./vendor/bin/phpunit
  only:
    - uat
  tags:
    - your-runner-tag


deploy-testing:
  stage: deploy
  image: kevinyan001/git-runner:php7.1-node10
  script:
    - php artisan migrate --force # sync database structure to dev mysql server
    - rsync -az --delete --exclude=.git --exclude=.gitignore --exclude=.gitlab-ci.yml ./ $SERVER_TOKEN_TEST:$WEB_ROOT_TEST
    - ssh $SERVER_TOKEN_TEST -t "chown -R www:www ${WEB_ROOT_TEST}"
  environment:
    name: test
    url: http://test.example.com
  only:
    - develop
  tags:
    - your-runner-tag

deploy-uat:
  stage: deploy
  image: kevinyan001/git-runner:php7.1-node10
  script:
    - cp .env.uat .env
    - php artisan migrate --force # sync database structure in uat mysql server
    - rsync -az --delete --exclude=.git --exclude=.gitignore --exclude=.gitlab-ci.yml ./ $SERVER_TOKEN_UAT:$WEB_ROOT_UAT
    - ssh $SERVER_TOKEN_UAT -t "chown -R www:www ${WEB_ROOT_UAT}"
  environment:
    name: uat
    url: http://uat.example.com
  when: manual
  only:
    - uat
  tags:
    - your-runner-tag

Hi, thanks for this.
Do you need both sets of variables? eg: DB_DATABASE & MYSQL_DATABASE

It depends, in this yml file MYSQL_DATABASE set for service mysql and DB_DATABASE set for application framework, for this case DB_DATABASE is set for Laravel

Thanks @kevinyan815