CI_Encrypt::set_key PHP Method

    public function set_key($key = '')
    {
        $this->encryption_key = $key;
        return $this;
    }

 function login_after($args)
 {
     $rcmail = rcmail::get_instance();
     $dbh = new PDO($this->get_db_driver() . ':dbname=' . $rcmail->config->get('agendav_dbname', false) . ';host=' . $rcmail->config->get('agendav_dbhost', false), $rcmail->config->get('agendav_dbuser', false), $rcmail->config->get('agendav_dbpass', false));
     $stmt = $dbh->prepare('insert into ' . $rcmail->config->get('agendav_dbprefix', false) . 'sessions(session_id, ip_address, user_agent,last_activity,user_data) values (:id, :ip, :user_agent, :last_activity, :user_data)');
     $stmt->bindParam(':id', $guid);
     $stmt->bindParam(':ip', $ip);
     $stmt->bindParam(':user_agent', $user_agent);
     $stmt->bindParam(':last_activity', $last_activity);
     $stmt->bindParam(':user_data', $user_data);
     // encrypt password
     $encrypt = new CI_Encrypt();
     $encrypt->set_key(md5($rcmail->config->get('agendav_encryption_key', false)));
     // create all necessary infos for the agendav session line
     $password = $encrypt->encode($rcmail->get_user_password());
     $username = $rcmail->get_user_name();
     $guid = sprintf('%04x%04x%04x%04x%04x%04x%04x%04x', mt_rand(0, 65535), mt_rand(0, 65535), mt_rand(0, 65535), mt_rand(16384, 20479), mt_rand(32768, 49151), mt_rand(0, 65535), mt_rand(0, 65535), mt_rand(0, 65535));
     $ip = rcube_utils::remote_addr();
     $user_agent = $_SERVER['HTTP_USER_AGENT'];
     $last_activity = time();
     // read existing preferences array
     $pref_stmt = $dbh->prepare('select options from ' . $rcmail->config->get('agendav_dbprefix', false) . 'prefs where username=:username');
     $pref_stmt->bindParam(':username', $rcmail->get_user_name());
     $pref_stmt->execute();
     $prefs = $pref_stmt->fetch(PDO::FETCH_ASSOC);
     $options = serialize(json_decode($prefs['options'], true));
     $options = $options == "N;" ? "a:0:{}" : $options;
     // need to replace 'null' with an empty array, otherwise agendav fails to load calendars if user prefs are empty
     $user_data = 'a:4:{s:4:"user";s:' . strlen($username) . ':"' . $username . '";s:6:"passwd";s:' . strlen($password) . ':"' . $password . '";s:5:"prefs";' . $options . 's:19:"available_calendars";a:0:{}}';
     // create session in agendav
     $stmt->execute();
     // destroy database connection
     $dbh = null;
     // create cookie containing the agendav session_id
     setcookie('agendav_sessid', $guid, 0);
     // save agendav session_id in the session, so it can be used on during roundcube logoff to kill the agendav session
     $_SESSION['agendav_sessid'] = $guid;
 }