PHP计算年龄精确到年月日

<?php

class CalAge {

    /*
     * 计算年龄精准到年月日
     * @param type $byear
     * @param type $bmonth
     * @param type $bday
     * @return type
     */
   public function getAge($byear, $bmonth, $bday) {
        $year = date(‘Y‘);
        $month = date(‘m‘);
        $day = date(‘d‘);
        $bmonth = intval($bmonth);
        $bday = intval($bday);
        if ($bmonth < 10) {
            $bmonth = ‘0‘ . $bmonth;
        }
        if ($bday < 10) {
            $bday = ‘0‘ . $bday;
        }
        $bi = intval($byear . $bmonth . $bday);
        $ni = intval($year . $month . $day);
        $not_birth = 0;
        if ($bi > $ni) {
            $not_birth =1;
            $tmp = array($byear, $bmonth, $bday);
            list($byear, $bmonth, $bday) = array($year, $month, $day);
            list($year, $month, $day) = $tmp;
            list($bi, $ni) = array($ni, $bi);
        }
        $years = 0;
        while (($bi + 10000) <= $ni) {//先取岁数
            $bi += 10000;
            $years++;
            $byear++;
        }//得到岁数后 抛弃年
        list($m, $d) = $this->_getMD(array($year, $month, $day), array($byear, $bmonth, $bday));
        return array($years, $m, $d, $not_birth);
    }

    /**
     * 只能用于一年内计算
     * @param type $ymd
     * @param type $bymd
     */
    private function _getMD($ymd, $bymd) {
        list($y, $m, $d) = $ymd;
        list($by, $bm, $bd) = $bymd;
        if (($m . $d) < ($bm . $bd)) {
            $m +=12;
        }
        $month = 0;
        while ((($bm . $bd) + 100) <= ($m . $d)) {
            $bm++;
            $month++;
        }
        if ($bd <= $d) {//同处一个月
            $day = $d - $bd;
        } else {//少一个月
            $mdays = $bm > 12 ? $this->_getMothDay(++$by, $bm - 12) : $this->_getMothDay($by, $bm);
            $day = $mdays - $bd + $d;
        }
        return array($month, $day);
    }

   private function _getMothDay($year, $month) {
        switch ($month) {
            case 1:
            case 3:
            case 5:
            case 7:
            case 8:
            case 10:
            case 12:
                $day = 31;
                break;
            case 2:
                $day = (intval($year % 4) ? 28 : 29); //能被4除尽的为29天其他28天
                break;
            default:
                $day = 30;
                break;
        }
        return $day;
    }

}

$ca = new CalAge();
echo ‘<pre>‘;
print_r($ca->getAge(‘2015‘, ‘09‘, ‘18‘));
echo ‘</pre>‘;