coffee2code

List the categories that are peer (i.e. share the same category parent) to all lowest-level assigned categories for the specified post.

This plugin provides a template tag which acts a modified version of WordPress’s built-in template tag, the_category(). the_category() lists all categories directly assigned to the specified post. peer_categories() lists those categories PLUS any categories that are peer to those categories and MINUS categories that are parents to other assigned categories. Peer categories are categories that all share the same category parent.

For example, assume your category structure is hierarchical and looks like this:

Vegetables
|-- Leafy
|   |-- Broccoli
|   |-- Bok Choy
|   |-- Celery
|-- Fruiting
|   |-- Bell Pepper
|   |-- Cucumber
|   |-- Pumpkin
|-- Podded
|   |-- Chickpea
|   |-- Lentil
|   |-- Soybean

If you directly assigned the categories “Fruiting” and “Pumpkin” to a post, peer_categories() would return a list that consists of: “Bell Pepper”, “Cucumber”, and “Pumpkin”. Notice that since “Fruiting” was a parent to a directly assigned category, it and its peers are not included in the list. If only “Fruiting” were selected as a category, then “Leafy”, “Fruiting”, and “Podded” would have been listed.

By default, categories are listed as an HTML list. The first argument to the template tag allows you to define a custom separator, e.g. to have a simple comma-separated list of peer categories: <?php peer_categories(','); ?>.

As with categories listed via the_category(), categories that are listed are presented as links to the respective category’s archive page.

Example usage (based on preceding example):

• <?php peer_categories(); ?>

Outputs something like:

<ul><li><a href="http://yourblog.com/category/fruiting/bell-pepper">Bell Pepper</a></li>
<li><a href="http://yourblog.com/category/fruiting/cucumber">Cucumber</a></li>
<li><a href="http://yourblog.com/category/fruiting/pumpkin">Pumpkin</a></li></ul>

• <?php peer_categories(','); ?></ul>

Outputs something like:

<a href="http://yourblog.com/category/fruiting/bell-pepper">Bell Pepper</a>, <a href="http://yourblog.com/category/fruiting/cucumber">Cucumber</a>, <a href="http://yourblog.com/category/fruiting/pumpkin">Pumpkin</a>

Links: Plugin Homepage | Plugin Directory Page | Author Homepage

Find out more at the plugin’s WordPress Plugin Repository page.

1. Unzip peer-categories.zip inside the /wp-content/plugins/ directory for your site (or install via the built-in WordPress plugin installer)
2. Activate the plugin through the ‘Plugins’ admin menu in WordPress
3. (optional) Add filters for ‘peer_categories’ to filter peer category listing
4. Use the template tag <?php peer_categories(); ?> somewhere inside “the loop”