Add to Post Type

You can add a taxonomy to any post type by passing the post type name to the posttype() method.

// Create the genre taxonomy.
$genres = new Taxonomy( 'genre' );
// Attach to the book post type.
$genres->posttype( 'books' );
// Register changes to WordPress.
$genres->register();

Alternatively, you can attach a taxonomy to a post type when creating a post type using its taxonomy() method.