title: Symfony2 (2.6.3), garbage collector and sessions
body: <p>I'm having a issue, just in Debian based distros, since at CentOS 6.6 it does not happen, and I don't know how to get rid of this other than set the property <code>gc_probability</code> to <code>0</code> which leads me to another issue. This is how my configuration looks at <code>config.yml</code>:</p>
  
  <pre><code>framework:
      session:
          # handler_id set to null will use default session handler from php.ini
          handler_id:  ~
          cookie_lifetime: 86400
          gc_maxlifetime: 600 # session will expire after 10 minutes of inactivity  
          gc_probability: 1
          gc_divisor: 1
  </code></pre>
  
  <p>That configuration in CentOS works perfectly as I said before but in Debian it fails with the following error:</p>
  
  <blockquote>
    <p>Notice: SessionHandler::gc(): ps_files_cleanup_dir:
    opendir(/var/lib/php5) failed: Permission denied (13)</p>
  </blockquote>
  
  <p>Why? What is the cause of this? </p>
  
  <p>Doing a research I found <a href="https://stackoverflow.com/questions/25454675/symfony-calls-the-php-garbage-collector-on-ubuntu-14-04-even-when-session-gc-pro">here</a> that disabling the value will makes the error goes out but then if I disabled that one the session never expires and the page could be opened for hours (I leave it open a complete night and the day after when I hit F5 surprise the same session with same values still open which is a security hole)</p>
  
  <p>Any advice around this? Solutions? Clues?</p>