PHP计算年龄

function age($YTD){
    $YTD = strtotime($YTD);
    $year = date(\'Y\', $YTD);
    if(($month = (date(\'m\') - date(\'m\', $YTD))) < 0){
        $year++;
    }else if ($month == 0 && date(\'d\') - date(\'d\', $YTD) < 0){
        $year++;
    }
    return date(\'Y\') - $year;
}