PHP--年龄转生日、生日转年龄

/**
     * 年龄转生日(模糊结果)
     * @parameter int age(年龄)
     * @parameter string symbol(分隔符)
     * @return string (yyyy*mm*dd)
     * @author he
     */
    private function agetobirthday($age,$symbol='-')
    {
        $age = $age==0?25:$age;
        $nowyear = date("Y",time());
        $year = $nowyear-$age;
        $monthArr = [];
        for ($i=1;$i<13;$i++){
            $monthArr[] = $i<10?'0'.$i:$i;
        }
        $dayArr = [];
        for ($i=1;$i<29;$i++){
            $dayArr[] = $i<10?'0'.$i:$i;
        }
        $month_key = array_rand($monthArr,1);
        $month = $monthArr[$month_key];
        $date_tmp_stamp = strtotime($year.'-'.$month);
        $day = '';
        if( $month=='02' && date("t",$date_tmp_stamp)=='29' ) {
            $dayArr = array_merge($dayArr,['29']);
            $day_key = array_rand($dayArr,1);
            $day = $dayArr[$day_key];
        } else if ( $month=='02' && date("t",$date_tmp_stamp)=='28' ){
            $day_key = array_rand($dayArr,1);
            $day = $dayArr[$day_key];
        } else if( in_array($month, ['01','03','05','07','08','10','12']) ) {
            $dayArr = array_merge($dayArr,['29','30','31']);
            $day_key = array_rand($dayArr,1);
            $day = $dayArr[$day_key];
        } else {
            $dayArr = array_merge($dayArr,['29','30']);
            $day_key = array_rand($dayArr,1);
            $day = $dayArr[$day_key];
        }
        return  $year.$symbol.$month.$symbol.$day;
    }
    
    /**
     * 生日转年龄
     * @author he
     * @parameter birthday:yyyy-mm-dd
     * @return str
     */
    private function birthdaytoage($birthday)
    {
        $age = 0;
        $year = date('Y',strtotime($birthday));
        $month = date('m',strtotime($birthday));
        $day = date('d',strtotime($birthday));
    
        $now_year = date('Y');
        $now_month = date('m');
        $now_day = date('d');
    
        if ($now_year > $year) {
            $age = $now_year - $year - 1;
            if ($now_month > $month) {
                $age++;
            } else if ($now_month == $month) {
                if ($now_day >= $day) {
                    $age++;
                }
            }
        }
        if(empty($birthday)){
            $age = 26;
        }
        return $age;
    }