How to show the category filter that's shown on the 'All post' pages on a custom post type page in the admin area?

Question

I suspect this is easy to do. but that I'm simply overlooking something somewhere in the documentation.

If you have your normal 'All posts' page in the admin area, then it shows 'Bulk Action', 'All dates' and 'All Categories'.

But not matter what I try when I create a custom post type, it always only shows the first two, so never the 'All Categories' dropdown ( categories do exist ). It must be possible to make that filter show up on the custom post type overview page in the admin area as well, right?

If someone can point me in the right direction, then that would be great.

Answer 1

If your post type supports the category taxonomy, then that drop-down menu would be displayed by default:

register_post_type( 'my_cpt', [
    'public'     => true,
    'taxonomies' => [ 'category' ], // here, the post type supports the `category` taxonomy
    //...
] );

Otherwise, or for custom taxonomies, you can use the restrict_manage_posts hook and wp_dropdown_categories() to add that drop-down menu. Working example:

// $which (the position of the filters form) is either 'top' or 'bottom'
add_action( 'restrict_manage_posts', function ( $post_type, $which ) {
    if ( 'top' === $which && 'my_cpt' === $post_type ) {
        $taxonomy = 'my_tax';
        $tax = get_taxonomy( $taxonomy );            // get the taxonomy object/data
        $cat = filter_input( INPUT_GET, $taxonomy ); // get the selected category slug

        echo '<label class="screen-reader-text" for="my_tax">Filter by ' .
            esc_html( $tax->labels->singular_name ) . '</label>';

        wp_dropdown_categories( [
            'show_option_all' => $tax->labels->all_items,
            'hide_empty'      => 0, // include categories that have no posts
            'hierarchical'    => $tax->hierarchical,
            'show_count'      => 0, // don't show the category's posts count
            'orderby'         => 'name',
            'selected'        => $cat,
            'taxonomy'        => $taxonomy,
            'name'            => $taxonomy,
            'value_field'     => 'slug',
        ] );
    }
}, 10, 2 );

And in that example, you'd only need to change the my_cpt (post type slug) and my_tax (taxonomy slug). But feel free to customize the code to your liking..