WordPress 3.0 custom post types, taxonomies & Thesis

With the recent launch of WordPress 3.0 there are loads of sweet new features to dig into. Digging into WordPress has a nice summary of many of the new features.

My favourite new features include the custom post types and custom taxonomies (which have been available for a while, but the dashboard management capability has been fully implemented now). I guess those are slightly more advanced features, I think most users may be more excited by backgrounds, header and menus. As such, Matt Hodder already has a great post about enabling WP 3.0 menus, backgrounds and headers in Thesis.

Also, there is an issue with the Thesis Custom File Editor in the dashboard, so if you use that a lot definitely check out the fix for the use_codepress() error.

Today I’m going to cover my favourite new WP 3.0 features.

Custom Taxonomies

Taxonomies are ways to classify posts and custom post types. WordPress has had two taxonomies for a long time: categories and tags. You’ve been able to register custom taxonomies in WordPress for quite a long time and since version 2.7 registering a non-hierarchical taxonomy (similar to tags) has provided a new input box in the post editing screen to assign your custom tag type to posts, but there was no menu item to edit that taxonomy and there was no input support for hierarchical taxonomies (like categories).

Now, registering a new taxonomy provides the input box on post editing pages and a dashboard menu item to edit the whole taxonomy.

Say you were building a website to document the spread of an infectious zombie-creating disease and wanted to profile and categorise individual zombies… You could create a custom post type for zombies (covered below) and assign location and infection taxonomies to make it easy to categorise and query where the zombies were sighted, or originated from, and which strain of the infection they have.

The following code would be posted into functions.php, or custom_functions.php for Thesis.

// === CUSTOM TAXONOMIES === //
function realestate_custom_taxonomies() {
	register_taxonomy(
		'location',		// internal name = machine-readable taxonomy name
		'zombie',		// object type = post, page, link, or custom post-type
		array(
			'hierarchical' => true,
			'label' => 'Location',	// the human-readable taxonomy name
			'query_var' => true,	// enable taxonomy-specific querying
			'rewrite' => array( 'slug' => 'location' ),	// pretty permalinks for your taxonomy?
		)
	);
	register_taxonomy(
		'infection',
		'post',
		array(
			'hierarchical' => false,
			'label' => 'Infection',
			'query_var' => true,
			'rewrite' => array( 'slug' => 'infection' ),
		)
	);

}
add_action('init', 'realestate_custom_taxonomies', 0);

The lines in the first registration are commented to explain them a bit, and another post by Justin Tadlock has some more details about custom taxonomies.

Notice that I made the Location taxonomy hierarchical, since I figured I could hone down the location as much as I want, and organise it in a hierarchy of country, state, city, suburb, etc. Also I only enabled it on “zombie” objects, that is, my Zombie post type. However, for the Infections tag I enabled it on posts because I figured I may write posts about the different strains and their evolution. I can enable the Infections taxonomy on Zombie post types within the post type registration below.

Custom Post Types

Custom post types are new in WP 3.0. They are like posts and pages, but are handled separately within the WordPress dashboard and by the regular post query — like pages, they don’t show up on the posts page or in the feed.

When creating custom post types you can call them whatever name you like and you can mix some of the features of posts and pages. For example, you can create a custom post type that is hierarchical (like pages, allowing child pages) and that uses categories, tags or custom taxonomies (like posts already do).

Justin Tadlock has an amazing post with the details of custom post types and how to make them. Refer to that post for all the parameters related to creating custom post types.

In Thesis, creating custom post types is not very different to any other theme. The main difference is that instead of adding the registration code to functions.php you add it to custom_functions.php.

// === CUSTOM POST TYPES === //
function create_my_post_types() {
	register_post_type( 'zombie',
		array(
			'labels' => array(
				'name' => __( 'Zombies' ),
				'singular_name' => __( 'Zombie' ),
				'add_new_item' => 'Add New Zombie',
				'edit_item' => 'Edit Zombie',
				'new_item' => 'New Zombie',
				'search_items' => 'Search Zombies',
				'not_found' => 'No zombies found',
				'not_found_in_trash' => 'No zombies found in trash',
			),
			'_builtin' => false,
			'public' => true,
			'hierarchical' => false,
			'taxonomies' => array( 'location', 'infection'),
			'supports' => array(
				'title',
				'editor',
				'excerpt',
				'custom-fields'
			),
			'rewrite' => array( 'slug' => 'zombie', 'with_front' => false ),
			//'register_meta_box_cb'=>'add_meta_boxes',
		)
	);
}
add_action( 'init', 'create_my_post_types' );

There are loads more parameters that you could use. I found that these were the ones I needed to create a pretty simple post type with a smooth experience (i.e., all the terms in the admin call the posts “zombie” or “zombies” appropriately, rather than “posts” or “pages”).

Worth noting is that even though the default slug (bit of the URL) will be the label (in this case “zombie”), I had to specifically state it in the registration code, otherwise I got a 404 error on my post. Also, you need to visit the permalink settings page after registering the post type to flush the rewrite rules so the new slugs work (just visit the page, you don’t have to re-save the options).

Thesis SEO & image metadata for custom post types

You might have noticed that the last line of my custom post type registration, //'register_meta_box_cb'=>'add_meta_boxes',, is commented out. Don’t uncomment it because it won’t work! To add meta boxes to the custom post type editing page, you need to provide a callback function and state the function name in the registration code. Thesis doesn’t support this yet, which is why I have custom fields enabled on the editing page. You can still use the Thesis SEO and image fields, but it will be a bit more manual until the callback is supported. I’ve left the line in the code to remind myself to add the callback in when it’s ready and I’ll edit this post to include it when it is.

If you’ve been using the Thesis fields then the keys will probably be available for you in a select box when adding a new custom field. Some of the values you will know what to do with, such as thesis_post_image and thesis_thumb just take an image URL, but if you’re not sure what values to use take a look at the custom fields on one of your older posts already using the Thesis meta to see what should be entered as the value for the field.

More to come

There’s a lot more to WordPress 3.0, but I think this post is long enough. I’m sure I and others will have more exciting things to come!