title: Why session expires automatically with codeigniter ? if use ajax calling on webpage
body: <p>I am new comer with php codeigniter session. i have a issue about session expiration on my site.
           I am using ajax coll for laoding advertizing div on our site page and also add to cart feature to add multiple products on same page. but my cart added products is empty due to session getting expired after appro. 4-5 minutes.
  I have done lot of study about this issue. i think my site session is expired due to colling ajax and updating session id at same time.But i am not sure for that.</p>
  
  <p><strong>I have configured config.php file like -</strong></p>
  
  <pre><code>$config['sess_cookie_name'] = 'ci_session';
  $config['sess_expiration']  = 0;
  $config['sess_encrypt_cookie']= FALSE;
  $config['sess_use_database']= TRUE;
  $config['sess_table_name']  = 'ci_sessions';
  $config['sess_match_ip']    = FALSE;
  $config['sess_match_useragent']= TRUE;
  $config['sess_time_to_update'] = 300;
  </code></pre>
  
  <p>I have also created table(ci_sessions).</p>
  
  <p><strong>Please give me a solution to fix this issue.</strong></p>
  
  <p>Thanks.</p>