In this comprehensive guide, we delve into a powerful feature of WordPress: Custom Taxonomy. This functionality empowers users to categorize and relate their WordPress content in innovative ways, offering unprecedented control over content organization. Although taxonomies were initially introduced in WordPress 2.3, they were significantly enhanced in WordPress 3.0, providing developers with a robust toolset.
Our recent exploration of custom WordPress post types laid the groundwork for understanding the nuances of WordPress 3.0 site and theme development. Now, we extend our knowledge by focusing on custom taxonomies. Essentially, a taxonomy is a method for organizing data, and in the context of WordPress, it serves as a framework for structuring and interlinking site content. You may already be familiar with one of WordPress’s built-in taxonomies: tags. Tags function as a taxonomy because they enable posts to be associated with them, viewed based on them, and organized through them.
Post categories represent another type of WordPress taxonomy. These features significantly enhance WordPress by enabling users to filter the information they wish to view on a site. A custom taxonomy is essentially a customized approach to linking together diverse content.
Custom taxonomies can be applied to both custom post types and regular pages and posts. Here are some examples of how custom taxonomies can be utilized:
– Release Year for movies
– Urgency levels such as “High Priority” or “Low Priority” for service bulletins
– Locations like room names, zip codes, or states for events
Each of these SEO-optimized taxonomies can assist in organizing information within a WordPress site. If you have read our guide on custom post types, the last example (events) will be familiar.
Building upon the Event custom post type introduced in our custom post types guide, we will now create a custom taxonomy called “Location.” This taxonomy will enable us to organize events based on their location.
Before proceeding, please note the following caveats: This guide will utilize the default TwentyTen theme included with WordPress 3 to ensure consistency among users. However, these instructions can be easily adapted for use with your own theme. Additionally, we will assume that you have followed our custom post types guide and have already created the custom Event post type.
WordPress simplifies the process of creating custom taxonomies, similar to custom post types. Let’s examine the code required to create the Location custom taxonomy:
“`php
add_action( ‘init’, ‘create_locations’ );
function create_locations() {
$labels = array(
‘name’ => _x( ‘Locations’, ‘taxonomy general name’ ),
‘singular_name’ => _x( ‘Location’, ‘taxonomy singular name’ ),
‘search_items’ => __( ‘Search Locations’ ),
‘all_items’ => __( ‘All Locations’ ),
‘parent_item’ => __( ‘Parent Location’ ),
‘parent_item_colon’ => __( ‘Parent Location:’ ),
‘edit_item’ => __( ‘Edit Location’ ),
‘update_item’ => __( ‘Update Location’ ),
‘add_new_item’ => __( ‘Add New Location’ ),
‘new_item_name’ => __( ‘New Location Name’ ),
);
register_taxonomy(‘location’,’event’,array(
‘hierarchical’ => true,
‘labels’ => $labels
));
}
“`
This code should be placed in the appropriate file within your theme’s directory.
The `register_taxonomy` WordPress function is responsible for creating the taxonomy. We will now explore the arguments passed to this function. The first argument is the internal name of our taxonomy, and the second argument specifies the post types that will utilize this taxonomy. In our case, we are linking it to our custom Event post type. You can replace this with `’post’` or `’page’` if you wish to use the taxonomy on posts and pages. You can also pass an array of multiple post types to allow various content types to use the taxonomy.
The last argument to `register_taxonomy` is a PHP array of options that informs WordPress how this taxonomy will operate. Let’s review the keys within the array argument.
The `’hierarchical’` key is a boolean that indicates whether the taxonomy has a hierarchy, meaning it has child categories or not. For our Location taxonomy, we will have a hierarchy. For instance, consider “Building 1, Conference Room A.”
Now that we have created the Location taxonomy, let’s log into WordPress and create some locations to be associated with our events.
Under the Events menu on the left-hand side of the administration screen, you will see a new link called “Locations.” Clicking on it will bring you to a screen where you can add, edit, and remove locations from the system. Create the following locations:
– Building 1
– Conference Room A
– Conference Room B
Once created, you should see your new locations listed in the Location table (next to the “Add Location” interface). Now that we have some locations, let’s add them to an Event post. Navigate to the “Add New Event” screen (or edit an existing event), and you should see a new Locations widget on the right-hand side.
This widget appears because, when we created the taxonomy, we instructed WordPress to associate it with the Event custom post type. Check off “Conference Room A” and then publish or save the event. You can add new locations directly from this screen if you find that one is missing.
This process is similar to that of WordPress post categories. If you create a non-hierarchical taxonomy, it will behave exactly like post tags. Now that we have created some locations and associated one with an Event post, we want to display each event’s location on the front-end of the site so readers can see them.
Next, we will cover how to display the Location taxonomy on individual event pages and configure a page template to show all events for a given location.
