修改预先存在的分类

Question

I have a theme that registers a flat taxonomy of tags and I need to convert it into a hierarchical taxonomy. Is there any way to modify a preexisting taxonomy (without editing my theme's files)?

Answer 1

There's a hook called register_taxonomy_args that should get you what you want. The constructor for the WP_Taxonomy object calls the method set_props which calls this hook very early on. Here's a quick (but untested) example:

add_filter(
    'register_taxonomy_args',
    static function (array $args, string $taxonomy, array $object_type) {
        if ('my-taxonomy' === $taxonomy) {
            $args['hierarchical'] = true;
        }
        return $args;
    },
    10,
    3
);