title: Symfony : Can't clear cache when using PHP global variable inside config.yml
body: <p>in my <code>config.yml</code> file, I import a <code>params.php</code> file which configures a parameter :</p>
  
  <pre><code>// app/config/params.php
  
  &lt;?php
  $container-&gt;setParameter('base_name', $_SERVER['BASE']);
  </code></pre>
  
  <p>I use this parameter for VichUploader configuration :</p>
  
  <pre><code>// app/config/config.yml
  imports:
      - { resource: parameters.yml }
      - { resource: security.yml }
      - { resource: services.yml }
      - { resource: params.php }
  
  vich_uploader:
     db_driver: orm
     mappings:
          tag_image:
              uri_prefix:         %base_name%/../images/tags
  </code></pre>
  
  <p>It works well in my project but I have an error when I want to clear cache :</p>
  
  <pre><code>$ php bin/console cache:clear
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/QN8es.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/QN8es.png" alt="enter image description here"></a></p>
  
  <p>I use Symfony3.
  I followed the guidelines of <a href="https://stackoverflow.com/questions/22219946/using-php-global-variable-inside-yml-file">this topic</a>.</p>