Fatal error: Class CI_Session_files_driver contains 1 abstract method
<blockquote>
  <p>Fatal error: Class CI_Session_files_driver contains 1 abstract method
  and must therefore be declared abstract or implement the remaining
  methods (SessionHandlerInterface::open) in
  C:\xampp\htdocs\cmms2\system\libraries\Session\drivers\Session_files_driver.php
  on line 49</p>
</blockquote>

<p>this error keeps on showing up while i'm working on my localhost xampp web app projec. I'm using codeigniter by the way. What do you think is the reason this shows up?
These are the only codes that I've done with session.</p>

<pre><code>  $this-&gt;session-&gt;set_userdata($data);
    $autoload['libraries'] = array('database','session');
    $config['sess_driver'] = 'files';
    $config['sess_cookie_name'] = 'ci_session';
    $config['sess_expiration'] = 7200;
    $config['sess_save_path'] = sys_get_temp_dir();
    $config['sess_match_ip'] = FALSE;
    $config['sess_time_to_update'] = 300;
    $config['sess_regenerate_destroy'] = FALSE;
</code></pre>