PHP - Composer: check if .json is valid and if .lock exists + is up to date

# Composer  https://getcomposer.org/doc/03-cli.md#validate
#           https://getcomposer.org/doc/03-cli.md#check-platform-reqs
# - checks that PHP and extensions versions match the platform requirements of the installed packages.
# - check if composer.json is valid
# - check if composer.lock exists and is up to date
composer_validate:
  stage: test
  script:
    - /usr/local/bin/composer check-platform-reqs
    - /usr/local/bin/composer validate