function is_numeric($var){

$str = (string)$var;

$int = (int)$var;

$strstr = (string)$int;

if($strstr==$str) return true;

else return false;

}

function check($year,$month,$day)

{

if(is_numeric($year) and is_numeric($month) and is_numeric($day)){

if(checkdate($month,$day,$year)){

echo $year . "年" . $month . "月" . $day . "日　是合法日期！
";

}

else{

echo $year . "年" . $month . "月" . $day . "日　不是合法日期！
";

}

}

else{

echo $year . "年" . $month . "月" . $day . "日　不是合法日期！
";

}

}

check("1999","1","1");

check("2000","2","31");

check("1900","2","1");

check("1900.2","2","1");

check("aaa","1","1");

?>