add current-cat class to single post page

Question

i know if you are on a category page..wp automatically ads current-cat class to the child of the parent category you are on.

like

`<li class="cat-item cat-item-701 current-cat"><a href="http://goog.com/cat/subcat">Free Stuff</a>
</li>`

how can i do this for a singlepost page.

I have the_category(); in the single.php file and it shows both parent and child category. I want to add a current-cat class to the child cat when i am on the single post page.

thanks in advance hopefully i did not confuse you.

Answer 1

the_category() uses get_the_category_list() to do its work, but this function gives you no way to specify classes. However, you can filter the output with the the_category hook. Since you know the format of the current category links, you can so a search and replace on them.

It would look something like this (untested):

add_filter('the_category', 'highlight_current_cats', 10, 3);
function highlight_current_cats($thelist, $separator, $parents)
{
    // The current cat links will look like <a href="[category link]" [other stuff]
    // We want them it look like <a href="[category link]" class="current-cat" [other stuff]
    $current_cats = get_the_category();
    if ($current_cats) {
        foreach ($current_cats as $cat) {
            $cat_link = get_category_link($cat->term_id);
            $thelist = str_replace('<a href="' . $cat_link . '"', '<a href="' . $cat_link . '" class="current-cat"', $thelist);
        }
    }
    return $thelist;
}