title: How does CodeIgniter know a cookie holds valid session data?
body: <p>In CodeIgniter, session data are saved in a cookie by default. But there must be also a file on my server (named as the session ID) to verify that the data (in the cookie) is valid, or am I wrong?</p>
  
  <p>I'm searching for the location where the sessions are saved. I've already looked in the "session.save_path" directory (/var/lib/php5), but in this directory there are only other sessions, but not the CodeIgniter sessions.</p>
  
  <p>I'm not saving the sessions in the database either, so how does CodeIgniter know that the data (in the cookie) is valid?</p>