php 根据生日计算年龄

// 根据出生日期求年龄
function getAgeByBirthday($val = "") {
    if($val == "") {
        return 45;
    }
    $tYear = date('Y');
    $tMonth = date('m');
    $tDay = date('d');
    $year = substr($val, 0, 4);
    $month = substr($val, 5, 2);
    $day = substr($val, 8, 2);
    $age = intval($tYear) - intval($year);
    if (intval($tMonth) < intval($month)) {
        $age -= 1;
    } else if(intval($tMonth) == intval($month) && intval($tDay) < intval($day)) {
        $age -= 1;
    }
    return $age;
}