Completely disable categories

Question

Is anyone aware of a plugin that disables categories in WP?

By this, I mean completely hiding the feature from view automatically, for existing and new users alike. In particular:

• the WP admin menu
• the posts list, its screen options, and its filters
• the post editor and its screen options
• the widgets screen
• the writing and permalink settings screens

I've run into a variety of aging hacks to do part of this, namely and mostly code to disable meta boxes and a handful of plugin to disable the permalink prefix. I'm turning to SO in the hopes that some web designer or developer might have the entire set of features on hand.

If not, might there be new APIs from the past 3-4 years that make the process simpler (my WP skills are getting rusty), or is seeing it through going to be an awkward output buffer manipulation-related hack?

Answer 1

With most credit due to this stackexchange answer:

function wpse120418_unregister_categories() {
    register_taxonomy( 'category', array() );
}
add_action( 'init', 'wpse120418_unregister_categories' );

This technically leaves everything in place (so you could bring it back at any time without a loss of data), but it "unhooks" it from everywhere in the admin by removing it from all $object_types.

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UPDATE

And to get rid of the Widget, add this to the function above.

unregister_widget( 'WP_Widget_Categories' );