title: Syntax error in Doctrine?
body: <p>We are working on our first site with Symfony. In development, everything works. But when we are on production, nothing works!
  Trying to use <code>app_dev.php</code>, we see:</p>
  
  <blockquote>
    <p>Parse error: syntax error, unexpected 'const' (T_CONST), expecting
    variable (T_VARIABLE)" in AbstractProxyFactory.php (line 72), script
    of Doctrine (in composer.json, we ask for Doctrine > 2.5)</p>
  </blockquote>
  
  <p>What does that mean?</p>