function saveReqData()
{
  $ip = isset($_SERVER['REMOTE_ADDR'])?$_SERVER['REMOTE_ADDR']:'';
  $user_agent = 
    isset($_SERVER['HTTP_USER_AGENT'])?$_SERVER['HTTP_USER_AGENT']:'';
  $referer = 
    isset($_SERVER['HTTP_REFERER'])?$_SERVER['HTTP_REFERER']:'';
  
  $query = "INSERT INTO visits VALUES"
         . "('$ip', '$user_agent', '$referer', CURRENT_TIMESTAMP)";
  
  $this->dbo->query($query);
}