<?
function isvaliddate($day, $month, $year) {
  $day = intval($day);
  $month = intval($month);
  $year = intval($year);
  $time = mktime(0,0,0,$month,$day,$year);
  if ($day != date("j",$time)) return false;
  if ($month != date("n",$time)) return false;
  if ($year != date("Y",$time)) return false;
  return true;
}
?>