title: How to use composer with php 7.2 with docker compose
body: <p>I'm trying to create a simple dev env for a web symfony app with docker compose. My problem is when trying to execute composer install I get this error:</p>
  
  <pre><code>- doctrine/collections v1.5.0 requires php ^7.1 -&gt; your PHP version (7.0.7) does not satisfy that requirement.
  </code></pre>
  
  <p>Here's the Composer part of my docker compose file:</p>
  
  <pre><code>composer:
          restart: 'no'
          image: composer/composer:php7
          command: install
          volumes:
             - .:/app
  </code></pre>
  
  <p>So that install a php 7.0 and I need at least 7.1. I tried with composer/composer:php7.1 but didn't work.</p>
  
  <p>Any idea on how to do this?</p>
  
  <p>Thanks in advance</p>