How does filtering work?

[musicmaster]

I am trying to figure out how filtering works.

 

In the database I see this kind of text as the implementation of a filter: 

a:6:{s:10:"categories";a:1:{i:0;i:100;}s:9:"shop_list";a:1:{i:0;i:1;}s:31:"layered_selection_subcategories";
a:2:{s:11:"filter_type";i:0;s:17:"filter_show_limit";i:4;}s:30:"layered_selection_manufacturer";a:2:{s:11:"filter_type";
i:1;s:17:"filter_show_limit";i:0;}s:24:"layered_selection_feat_5";a:2:{s:11:"filter_type";i:2;s:17:"filter_show_limit";i:0;}
s:24:"layered_selection_feat_8";a:2:{s:11:"filter_type";i:0;s:17:"filter_show_limit";i:0;[spam-filter]

Does anyone know what it means or where I can find what it means?

Edited December 28, 2013 by musicmaster (see edit history)

[Piotr Kaczor]

It's serialized array() when PHP grab it from DB it run unserialize() function:

<?php
$a = unserialize('a:6:{s:10:"categories";a:1:{i:0;i:100;}s:9:"shop_list";a:1:{i:0;i:1;}s:31:"layered_selection_subcategories";a:2:{s:11:"filter_type";i:0;s:17:"filter_show_limit";i:4;}s:30:"layered_selection_manufacturer";a:2:{s:11:"filter_type";i:1;s:17:"filter_show_limit";i:0;}s:24:"layered_selection_feat_5";a:2:{s:11:"filter_type";i:2;s:17:"filter_show_limit";i:0;}s:24:"layered_selection_feat_8";a:2:{s:11:"filter_type";i:0;s:17:"filter_show_limit";i:0;[spam-filter]');
echo '<pre>';
print_r($a);
?>

// so it got that array
Array
(
    [categories] => Array
        (
            [0] => 100
        )

    [shop_list] => Array
        (
            [0] => 1
        )

    [layered_selection_subcategories] => Array
        (
            [filter_type] => 0
            [filter_show_limit] => 4
        )

    [layered_selection_manufacturer] => Array
        (
            [filter_type] => 1
            [filter_show_limit] => 0
        )

    [layered_selection_feat_5] => Array
        (
            [filter_type] => 2
            [filter_show_limit] => 0
        )

    [layered_selection_feat_8] => Array
        (
            [filter_type] => 0
            [filter_show_limit] => 0
        )

)

Edited December 28, 2013 by Piotr Kaczor (see edit history)