Editing "Kahi's Highlight Used Categories" plugin code - highlighting parent and child category in post page

Question

I´m trying to highlight (using css), the child and parent categories in use in the selected post.

So I´ve found this plugin "Kahi's Highlight Used Categories".

Plugin´s website: http://kahi.cz/wordpress/highlight-used-categories-plugin/

What it does...

It adds a 'used-cat' class and 'used-cat-parent' class to stylize, to the sub-category and main category respectively.

The problem is:

My website (http://www.mpn.p.ht/wp_br2/), has three main categories "Masculino", (means male), "Feminino", (means female), and "Infantil", (means infant).

The sub-categories are the same for all the three main categories.

So, let´s say, we are at the post page with main category "Masculino", and sub-category "Acessórios", (means acessories)...

The plugin, seems to add 'used-cat' to all "Acessórios" (sub-category), found also in "Feminino" , and in "Infantil".

I would like the plugin to add the class 'used-cat', only to the sub-category of the selected post. Not to all sub-categories found with the same name, through the categories list.

Here´s the plugin code:

<?php
/*
Plugin Name: Kahi's Highligh Used Categories
Plugin URI: http://www.kahi.cz/wordpress/highlight-used-categories-plugin
Description: In the list of categories, adds classes <code>used-cat</code> and 
<code>used-cat-parents</code> to particular list-items (when browsing a post).

Version: 1.0
Author: Peter Kahoun and Dirk Jaster
Author URI: http://www.kahi.cz/wordpress/
*/

class KHUC {

function wp_list_categories ($text) {

    global $post;

    if (is_singular()) {

        $categories = wp_get_post_categories($post->ID);

        foreach ($categories as $category_id) {

            $category = get_category($category_id);
            $category_parent = get_category($category->category_parent);

            $text = preg_replace(
                "/class=\"(.*)\"><a ([^<>]*)>$category->name<\/a>/", 
                ' class="$1 used-cat"><a $2>' . $category->name .    
'</a>', 
                $text);

            $text = preg_replace(
                "/class=\"(.*)\"><a ([^<>]*)>$category_parent-
>name<\/a>/", 
                ' class="$1 used-cat-parent"><a $2>' . 
$category_parent->name . '</a>', 
                $text);

        }

    }

    return $text;

}

}

add_filter('wp_list_categories', array('KHUC','wp_list_categories'));

Does anyone know, what changes in the plugin code should I make, so I get only the sub-category in use to get the 'used-cat' class?

Answer 1

Use the category ID:

class KHUC {
    function wp_list_categories ($text) {
        global $post;
        if (is_singular()) {
            $categories = wp_get_post_categories($post->ID);
            foreach ($categories as $category_id) {
                $category = get_category($category_id);
                $category_parent = get_category($category->category_parent);
                $text = preg_replace(
                    '#class="([^"]*cat-item-'.$category->cat_ID.'[^"0-9]*)"#',
                    'class="$1 used-cat"', 
                    $text);
                $text = preg_replace(
                    '#class="([^"]*cat-item-'.$category_parent->cat_ID.'[^"0-9]*)"#',
                    'class="$1 used-cat-parent"', 
                    $text);
            }
        }
        return $text;
    }
}
add_filter('wp_list_categories', array('KHUC', 'wp_list_categories'));