PHP calculates age (years old) based on birthday

<?php/**
 * 根据时间戳计算年龄
 * @param $birth
 * @return mixed
 */functionhowOld($birth) {list($birthYear, $birthMonth, $birthDay) = explode(&#39;-&#39;, date(&#39;Y-m-d&#39;, $birth));
    list($currentYear, $currentMonth, $currentDay) = explode(&#39;-&#39;, date(&#39;Y-m-d&#39;));
    $age = $currentYear - $birthYear - 1;
    if($currentMonth > $birthMonth || $currentMonth == $birthMonth && $currentDay >= $birthDay)
        $age++;

    return$age;
}
?>