Howto : not display child categories’ posts in parent category archive

hi i post this ‘cos it’s a way to refresh an old post i found on this forum http://wordpress.org/support/topic/71767
and some of you may be interested…
Well, the goal is that each category displays only its own posts and not those of its child categories.

here you go:
(this in WP v.2.0.4, line numbers may change in further versions)

1. open wp-includes/classes.php
2. just insert // at the very beginning of these lines – or destroy them:
   line 473
   $whichcat .= get_category_children($cat_array[0], ' '.$andor.' category_id '.$eq.' ');

   line 476
   $whichcat .= get_category_children($cat_array[$i], ' '.$andor.' category_id '.$eq.' ');

   line 514
   $whichcat .= get_category_children($q['cat'], " OR category_id = ");

You’re done! Code is poetry, as they say!

You may then want to do the same with
wp-includes/wp-includes/template-functions-category.php
(the changes below are OPTIONAL)

line 201
$query .= get_category_children($hide, " AND cat_ID != ");

And: lines 128-145:

1- insert /* at the beginning of line 128
2- insert */ line 145

128-145:
function get_category_children($id, $before = '/', $after = '') {
if ( 0 == $id )
return '';
$cat_ids = get_all_category_ids();
foreach ( $cat_ids as $cat_id ) {
if ( $cat_id == $id)
continue;
$category = get_category($cat_id);
if ( $category->category_parent == $id ) {
$chain .= $before.$category->cat_ID.$after;
$chain .= get_category_children($category->cat_ID, $before, $after);
}
}
return $chain;
}