Displaying Other Posts in the Category Hierarchy in WordPress

On several pages, including a category archive page (and in the category feed), WordPress by default shows posts in that category and its child or sub-categories.

What if you want to change which posts are included? Use the pre_get_posts filter to modify the query sent to the database and customise what posts are displayed. Here are some functions to add to your theme’s functions.php file.

Exclude A Specific Category

To exclude a specific category with category id ‘xx’ from the home page:

function exclude_category($query) {
	if ($query->is_home) {
		$query->set('cat', '-xx');
	}
	return $query;
}

add_filter('pre_get_posts', 'exclude_category');

Exclude Multiple Categories

Separate multiple categories with spaces. E.g. to exclude categories with ids ‘xx’, ‘xy’ and ‘xz’, change line 3 in the above to:

$query->set('cat', '-xx -xy -xz');

Include Categories

To include a single category with id ‘xx’, change line 3 in the above to:

$query->set('cat', 'xx');

To include multiple categories with ids ‘xx’, ‘xy’ and ‘xz’, change line 3 in the above to:

$query->set('cat', 'xx xy xz');

Exclude Child Categories

To show only the posts in the selected category and not those in its descendent categories add the following to functions.php:

function exclude_child_cats($query){
	if ($query->is_category){
		$this_category=get_query_var('cat');
		$child_cats=get_categories(array('parent' => $this_category));
		$this_category.=' ';
		foreach($child_cats as $child_cat){
				$this_category.='-'.$child_cat->cat_ID.' ';
		}
		$query->set('cat', $this_category);
	}
}

add_filter('pre_get_posts','exclude_child_cats');

Other Pages You Can Test For

So far the examples have test whether the current page is the home page, using if($query->is_home), or a category archive page, using if($query->is_category). Here is a list of all the query types you can test for:

is_single
is_page
is_archive
is_date
is_year
is_month
is_day
is_time
is_author
is_category
is_tag
is_tax
is_search
is_feed
is_comment_feed
is_trackback
is_home
is_404
is_paged
is_admin
is_attachment
is_singular
is_robots
is_posts_page

These Changes Affect Your Feeds

So you want these same changes to your feed too? – Done!

WordPress generates your feeds ‘on-the-fly’, using the same query as for displaying your site in a browser. Therefore any changes you make using this method also apply to your feeds. Very cool!

UPDATE: This system works great if you are using the default permalinks settings, but will not work with “Pretty Permalinks”!

Hannah Napier