The image is for running codesniffer, codesniffer is installed in /app/ in case you need to customize the install before usage. Default the following packages are installed:
.
phpcs PSR2:
  stage: linting
  image: registry.gitlab.com/pipeline-components/php-codesniffer:latest
  script:
    - phpcs -s -p --colors --extensions=php --standard=PSR2 .
php-compatibility 7.3:
  stage: test
  image: registry.gitlab.com/pipeline-components/php-codesniffer:latest
  variables:
    PHPVERSION: "7.3"
  script:
    - >-
      phpcs -s -p --colors
      --standard=PHPCompatibility
      --extensions=php
      --runtime-set testVersion ${PHPVERSION} .