Linking Taxonomies

Question

I currently have two post types, Posts and Tutorials. Tutorials are grouped into sets of tutorials within Courses, which I have created with a custom Course taxonomy. Courses can belong to multiple categories, as can Posts. These categories have been created using the built-in category taxonomy. Posts will never belong to a course and should have no association to them.

How can I set up this hierarchy, primarily the linking of a custom Course taxonomy to the built-in Category taxonomy?

Answer 1

When you register your custom post type you can set which taxonomies will be registered for this post type. So you can register your custom 'Course' taxonomy and the built-in 'Category' taxonomy with your custom post type 'Tutorials'. And posts will just be registered with 'Category'.

function tutorial_setup_post_type() {
    $args = array(
        'public'    => true,
        'label'     => __( 'Tutorials', 'textdomain' ),
        'taxonomies' => array(
            'category',
            'course'
        ),
    );
    register_post_type( 'tutorial', $args );
}
add_action( 'init', 'tutorial_setup_post_type' );

https://developer.wordpress.org/reference/functions/register_post_type/