php 计算年龄

// 计算年龄
    function birthday($birthday){
        $age = strtotime($birthday);
        if($age === false){
            return false;
        }
        list($y1,$m1,$d1) = explode("-",date("Y-m-d",$age));
        $now = strtotime("now");
        list($y2,$m2,$d2) = explode("-",date("Y-m-d",$now));
        $age = $y2 - $y1;
        if((int)($m2.$d2) < (int)($m1.$d1))
            $age -= 1;
        return $age;
    }