title: Environment variable assignment in Docker Compose - colon way
body: <p>This is the question about docker-compose.yml file syntax. I met the variable assignment like this on the internet:</p>
  
  <pre class="lang-yaml prettyprint-override"><code>environment:
      PMA_HOST: mysql
  </code></pre>
  <p><a href="http://tech.osteel.me/posts/2017/01/15/how-to-use-docker-for-local-web-development-an-update.html" rel="noreferrer">http://tech.osteel.me/posts/2017/01/15/how-to-use-docker-for-local-web-development-an-update.html</a></p>
  <hr />
  <p>On the other hand the documentation tells like this:</p>
  <pre class="lang-yaml prettyprint-override"><code>environment:
    - DEBUG=1
  </code></pre>
  <p><a href="https://docs.docker.com/compose/environment-variables/" rel="noreferrer">https://docs.docker.com/compose/environment-variables/</a></p>
  <p>Is the way without the dash and with the colon proper? What is the difference?</p>