Custom Taxonomies in WordPress 2.8

There has been a bit of talk about “custom taxonomies” in WordPress, which have been around since version 2.3, and how WordPress 2.8 will integrate them into the interface in some amazing, better-than-sliced-bread way.

Many of the posts out there, unfortunately, never explained in a clear manner what custom taxonomies were. They talked of how amazing the concept was, and things like that, but they didn’t lay out the concept so people could understand the concept.

Justin Tadlock has a comprehensive post, Custom taxonomies in WordPress 2.8, that explains the concept very well, and has pretty much everything you need to know. What’s coming in 2.8, what’s already in WP, code snippets illustrating the use of the Custom Taxonomy API, etc.

By default, WordPress comes pre-loaded with three taxonomies: category, post_tag, and link_category. The first two allow us to label our posts a certain way. The last lets us categorize our links. I’ll be showing you how to easily create your own and use them in this tutorial.

Each taxonomy has what are called terms. For example, all of your tags are actually terms that live within the post_tag taxonomy.

Essentially, custom taxonomies are groups of tags. Suppose you run a movie review blog. You could create a taxonomy for “Actors,” and WordPress 2.8 will add an “Actors” box to the Write Post page, where you can assign a term (i.e. tag) for each of the actors in the movie.

This will be very useful for large sites with more advanced functionality or massive amounts of content that need to be indexed thoroughly. You could turn WordPress into an IMDB clone without too much effort.