PHP常用函数系列--根据生日计算年龄

/**
 * 根据出生年月日计算出年龄
 * @param $birth_year 
 * @param $birth_month
 * @param $birth_day
 * @return int
 */
function getAgeByBirth($birth_year,$birth_month,$birth_day){
    if(empty($birth_year) || empty($birth_month) || empty($birth_day)){
        return 0;
    }
    $current_year = date('Y',time());
    $current_month = date('m',time());
    $current_day = date('d',time());
    if($birth_year >= $current_year){
        return 0;
    }
    $age = $current_year - $birth_year - 1;
    if($current_month>$birth_month){
        return $age+1;
    }else if($current_month == $birth_month && $current_day>=$birth_day){
        return $age+1;
    }else{
        return $age;
    }
}