检索数据库wordpress中的序列化值

I'm trying to query a serialized array value in the database in wordpress, value will be stored in the table wp_postmeta, in the column meta_value.
Well, first I stored the array by using serialize() function of php.
So for example,

$postID = 1;
$arr = array(1, 2, 3);
$ser_val = serialize($arr);
update_meta_data($postID, '_customvalue', $ser_val);

The stored values is something like this

s:30:"a:3:{i:0;i:1;i:1;i:2;i:2;i:3;}";

Then when I tried to retrieve it by performing wordpress sql query.. What I was expecting that it will be an array since it is stored as array, but after doing so, it display as string not an array.

    $get_score = $wpdb->get_row("SELECT meta_value FROM wp_postmeta WHERE meta_key = '_cummulativescore'");
    $scr = unserialize($get_score->meta_value);
    var_dump($scr);

    //output displayed
    //string(30) "a:3:{i:0;i:1;i:1;i:2;i:2;i:3;}" 

I did check the value using is_array() function, the result is that it is not an array
Any idea on this to get the serialize value as an array?

It looks like your data was converted to a string during serialization.

The data should be stored as

a:3:{i:0;i:1;i:1;i:2;i:2;i:3;}

instead of

s:30:"a:3:{i:0;i:1;i:1;i:2;i:2;i:3;}"

s:30 means string length 30.