Thanks for providing this solution.
You should submit it to WP because it is a valuable and quite used function. For me, you saved the day !!!

Kudos!

does it work also with category-slugs?

thank you

I think Trau’s problem (emphasis on i*I think*, I probably should try it first) might have to do with the categories the current post was assigned to. What I mean is.. when that post was added, it could have been assigned both the parent and child category in the Categories box ( via checking both the parent and child boxes)

Unless that’s the proper way of doing that?

It can’t be, right? However, for example, when if setup my permalink structure as so:

/%category%/%postname%/

I end up with the permalink of my child category posts showing only the parent category while /%category%/ is supposed generate the nested directory for the sub category.

-C

Second, I use this function on almost every site I’ve ever built and it has always worked fine. I’m not sure why you are having difficulty but there is no reason I can think of that you would need to edit the original function.

I’m glad you got it to work anyhow.

and modifie the function “is_category_or_sub” with parameter $this_category and this work!!
thx a lot!
:)
good blog
regard
erwin

i have put this code:
// If is category or subcategory of $cat_id
if (!function_exists(‘is_category_or_sub’)) {
function is_category_or_sub($cat_id = 0) {
foreach (get_the_category() as $cat) {
if ($cat_id == $cat->cat_ID || cat_is_ancestor_of($cat_id, $cat)) return true;
}
return false;
}
}

if (is_category_or_sub(1)) {
echo “DISPLAY 1″;
} else {
echo “DISPLAY 2″;
}

in page archive.php

but i see string “DISPLAY 2″ in booth category and subcategory why?
i have put this code before in archive page.
Can you help me please?where i wrong?
regard erwin

ps sorry my bad english :P