class CI_Session {

 var $sess_encrypt_cookie  = FALSE;
 var $sess_use_database   = FALSE;
 var $sess_table_name   = '';
 var $sess_expiration   = 7200;
 var $sess_expire_on_close  = FALSE;

             중략....

        public function __construct($params = array())
        {
             중략....
             $this->_sess_gc();
        }


         /**
  * Garbage collection
  *
  * This deletes expired session rows from database
  * if the probability percentage is met
  *
  * @access public
  * @return void
  */
 function _sess_gc()
 {
     if ($this->sess_use_database != TRUE)
     {
        return;
     }

     srand(time());
     if ((rand() % 100) < $this->gc_probability)
     {
        $expire = $this->now - $this->sess_expiration;
        $this->CI->db->where("last_activity < {$expire}");
        $this->CI->db->delete($this->sess_table_name);
        log_message('debug', 'Session garbage collection performed.');
     }
  }
}