Custom Post Type categories at edit post not hierarchical

Question

I have created a custom post type and added a custom taxonomy like this:

register_taxonomy(
    'categories',
    'ph_products',
    array(
        'hierarchical' => true,
        'show_admin_column' => true,
        'label' => 'Products',
        'query_var' => true,
        'rewrite' => array(
            'slug' => 'products',
            'with_front' => false
        )
    )
);

When I create some categories and child categories it looks right. But when I switch to create a post all the categories are on one level and not indented. So it seems its just a problem in the edit post page. For normal posts the hierarchies are displayed correctly in the sidebar when creating a new post.

What am I missing?

Answer 1

It might be because you are using reserved term name as first argument; 'categories' is wordpress core taxonomy and you should use something else like 'ph_categories'. After that you will have to add those terms again.

Reference: Codex