Adding a Show All button to a taxonomy filter

Tips
1

As it has been requested, here is our clean and simple solution to adding a Show All button for taxonomy filters.

Steps:

  1. For the built-in taxonomies (such as Category), you can rename the default term name to “Show All” and the slug to “all”. When creating a custom taxonomy you want to have a Show All button for, add a default term. In ACF this can be done using the following setting:

Screenshot 2024-09-26 at 20.31.27
Screenshot 2024-09-26 at 20.31.271580×1326 159 KB

  1. Then add the following code snippet - change $post_types and $taxonomies to match your requirements:
function auto_add_post_taxonomy_term( $post_ID ) {
	$post_types = ['article']; // The post types you want to apply this to
	$taxonomies = ['article-category', 'industry', 'region']; // The taxonomies to display Show All for
	$current_post_type = get_post_type($post_ID);
	$term_slug = 'all';

	if(in_array($current_post_type, $post_types)) {
		foreach ($taxonomies as $taxonomy) {
			$term_obj = get_term_by('slug', $term_slug, $taxonomy);

			$post_terms = wp_get_object_terms( $post_ID, $taxonomy );

			if (!in_array($term_obj, $post_terms)) {
				wp_add_object_terms($post_ID, $term_slug, $taxonomy);
			}
		}
    }

   return $post_ID;
}
add_action( 'save_post', 'auto_add_post_taxonomy_term' );

Important notes:

  1. If you have multiple post types and want different taxonomies to apply to each of them, you will have to adjust the code snippet accordingly.
  2. To add the code snippet please see the following tip:

I hope this saves you some time and helps you to do this more easily.

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