Taking advantage of the template_include filter

If you are like me, you often want to control what template file WordPress uses. Some of the methods I’ve seen around the internet try to use template_redirect. Others are even worse and employ sticking tons of conditionals inside WordPress template files (eg category.php).

Well I am here to tell you there is a much easier way. It’s fairly unknown and sparsely documented. It’s the template_include filter.

The use cases for template_include are endless but I will give you a great example where I recently took advantage of it.

Let’s say you have a category structure like below:

• Audio
• News
• Local
• Health
• Technology
• Sports
• Politics
• Travel
• Videos

Looks straight forward, right? Using the normal WordPress template hierarchy you can easily target these categories. We all know category-news.php would be used when viewing the News category or category-health.php would take care of the Health category.

However, what if you want to create a unique template for all the News sub-categories? Here are the two options you will usually find.

1. Create a category.php file and use conditionals to target the individual sub categories. Lame!
2. Create a template file for each sub-category (category-local.php, category-health.php, etc). Even more lame!

I want to have one template file that will be used for all the News sub-categories, not conditionals or duplicate scattered everywhere. With single snippet (which would be in functions.php) using the template_include filter this can be done!

<?php
add_filter( 'template_include', 'ja_template_check' );
function ja_template_check() {
	global $template;

	if ( is_category() ){

		// Get category information
		$cat = get_query_var( 'cat' );
		$category_info = get_category( $cat );

		// News sub-categories, where 7 is the ID for News
		if ( $category_info->parent == 7 ){
			$template_file = get_stylesheet_directory_uri() . '/subcategory-news.php';
			return $template_file;
		}
	}
	return $template;

}

The code above first checks to see if you are looking at a category. If that is true it then checks to see if the parent category ID is 7. Finally, if this checks out it uses a template file I created,  subcategory-news.php.

Pretty easy, right?

Props to @wpmuguru for sending me in this direction.