class TimeInterval
{
  public function __construct($seconds){ *** }

  public function addSeconds($count){ ***** += $count; }
  public function addMinutes($count){ ***** += $count * 60; }
  public function addHours($count){ ***** += $count * 60 * 60; }

  public function getSeconds(){ *** }
  public function getMinutes(){ *** }
  public function getHours(){ *** }
}