PHP计算年龄的函数

今天工作要计算用户的生日到周，找到一个函数。

 

/**
     *  计算生日到现在的时间
     * @param int $birthday    宝贝生日
     */
    function age($birthday) {
        $now = date('Ymd');
        //分解当前日期为年月日
        $y = (int) ($now / 10000);
        $m = (int) (($now % 10000) / 100);
        $d = $now % 100;
        //分解生日为年月日
        $yy = (int) ($birthday / 10000);
        $ym = (int) (($birthday % 10000) / 100);
        $yd = $birthday % 100;
        //特殊日期计算
        if ($years % 4 == 0 || ($years % 100 == 0 && $years % 400 == 0)) {
            $special = 29;
        } else {
            $special = 28;
        }
        //各月的上个月的天数
        switch ($m) {
            case 2:$add = 31;
            case 3:$add = 31;
            case 6:$add = 31;
            case 8:$add = 31;
            case 9:$add = 31;
            case 11:$add = 31;
            case 1:$add = 31;
            case 5:$add = 30;
            case 7:$add = 30;
            case 10:$add = 30;
            case 12:$add = 30;
            case 3:$add = $special;
        }
        if ($d < $yd) {
            $d+=$add;
            $m-=1;
        }
        if ($m < $ym) {
            $m+=12;
            $y-=1;
        }
        //运算年龄
        if ($now >= $birthday) {
            $age['day'] = $d - $yd;
            $age['month'] = $m - $ym;
            $age['year'] = $y - $yy;
            return $age;
        }else{
            return 0;
        }
    }