title: Session data gone after redirect in CI
body: <p>i need your help.
  I used the session to record the user selected business type in CI. For example,$this->ci->session->set_userdata('biztype','food'). When user login,it works ok. However, once the user logout, session will be destroyed in the function logout().So i set the userdata again in the function logout().You can view the code below:</p>
  
  <pre><code>function logout()
  {
    $biztype = $this-&gt;ci-&gt;session-&gt;userdata('biztype');
    $this-&gt;delete_autologin();
  
    $this-&gt;ci-&gt;session-&gt;set_userdata(array('user_id' =&gt; '', 'username' =&gt; '', 'status' =&gt;  ''));
  
    $this-&gt;ci-&gt;session-&gt;sess_destroy();
    $this-&gt;ci-&gt;session-&gt;set_userdata('biztype',$biztype);
    //echo $this-&gt;ci-&gt;session-&gt;userdata('biztype');   //here, i can get biztype that i want
  }
  </code></pre>
  
  <p>However,when i logout and redirect to homepage, i cant get the userdata('biztype') and my session_id have changed.
  Thanks for the help.</p>