title: Symfony parameters variable in variable
body: <p>I work on a symfony project and I want to do something like this in my app/config/parameters.yml</p>
  
  <pre><code>dev.google.api.key: foo
  google: %%kernel.environment%.google%
  </code></pre>
  
  <p>It not works.</p>
  
  <p>I explain : I want to have the variable google to have values depending my environment (env or prod).</p>
  
  <p>So I defined two variable :</p>
  
  <pre><code>dev.google.api.key: foo
  prod.google.api.key: bar
  </code></pre>
  
  <p>I want to have my variable google to be filled with content depending on the environment. The environment is in the variable </p>
  
  <pre><code>%kernel.environment%
  </code></pre>
  
  <p>So if I do :</p>
  
  <pre><code>google: %kernel.environment%.google
  </code></pre>
  
  <p>Google is equal to "dev.google" but I want to this string to be evaluated like this %dev.google%. But %%kernel.environment%.google% not works.</p>
  
  <p>An idea ?
  Thanks</p>