Add post classes for custom taxonomies to custom post type?

I was surprised to learn that custom taxonomies aren’t added as body or post classes like categories and tags are.

I’m sure this will be added in a future version of WordPress, but in the meantime I need to add a custom taxonomy to the post class so that I can style post in a certain category in that taxonomy differently.

It’d be most elegant to filter the post class and add the taxonomies to it. I found a snippet to pull off a similar trick with the body class, but I haven’t been successful in adapting it:

function wpprogrammer_post_name_in_body_class( $classes ){
 if( is_singular() )
  global $post;
  array_push( $classes, "{$post->post_type}-{$post->post_name}" );
 return $classes;

add_filter( 'body_class', 'wpprogrammer_post_name_in_body_class' );

A bit more crudely, I thought about using the_terms function to create my own classes for the custom posts, something like this:

<div class="<?php the_terms( $post->ID, 'taxonomy', '', ' ', '' ); ?>"></div>

But then I’d have to filter out the HTML that the_term generates.

Am I missing anything obvious here, is there a simpler way to solve this issue?

5 s

I found a snippet of code courtesy of mfields that solved this problem for me, here’s what I ended up using:

<?php   // Add custom taxonomies to the post class

    add_filter( 'post_class', 'custom_taxonomy_post_class', 10, 3 );

    if( !function_exists( 'custom_taxonomy_post_class' ) ) {

        function custom_taxonomy_post_class( $classes, $class, $ID ) {

            $taxonomy = 'listing-category';

            $terms = get_the_terms( (int) $ID, $taxonomy );

            if( !empty( $terms ) ) {

                foreach( (array) $terms as $order => $term ) {

                    if( !in_array( $term->slug, $classes ) ) {

                        $classes[] = $term->slug;




            return $classes;


    }  ?>

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