Remove child category from URL

Question

I am moving a custom website with a WP blog to WP in one install

The old URL was: domain.co.uk/blog/post-name

The New URL is currently (while using a Category URL rewrite of /%category%/%postname%/ ) domain.co.uk/blog/category/post-name

Is there a way to remove the child category from the URL so it will be the same as the the old URL (so I don't need to 301 redirect all the old url's)

The client still wants the posts to be categorised hence the need for the custom permalink

Answer 1

You can use the post_link_category filter to remove child categories from permalinks:

function wpse147453_remove_child_categories_from_permalinks( $category ) {
    while ( $category->parent ) {
        $category = get_term( $category->parent, 'category' );
    }

    return $category;
}
add_filter( 'post_link_category', 'wpse147453_remove_child_categories_from_permalinks' );