title: PHP sessions that have already been started
body: <p>In my PHP code, if a session has already started, and I try to start a new one, I get the following Notice:</p>
  
  <blockquote>
    <p>Notice: A session had already been started - ignoring session_start()</p>
  </blockquote>
  
  <p>How can I avoid this?</p>