How do you add a category to a post in code

Question

We do a lot of post maintenance outside of the WordPress interface and as a result we need ways of categorising posts. Obviously Wordpress has categories (aka taxonomies) on posts and I plan on using them, but haven't found a way that I can do that in code.

We also use custom post types extensively so the accepted answer may need to state how to incorporate categories into them.

Answer 1

There's the wp_update_post(), also.

According to categories, please refer to the documentation.

Categories need to be passed as an array of integers that match the category IDs in the database. This is the case even where only one category is assigned to the post.

So, it would be something like:

$post = get_post($i = $post_id);
$post->post_category = array ($cat1, $cat2, $cat3);
wp_update_post($post);

Answer 2

You should be able to do just about everything you're looking to do between wp_insert_post(), wp_set_object_terms(), and wp_insert_term(). Those all work well with custom post types and custom taxonomies. If you can be a bit more specific about any issues you're encountering (possibly in a new question...depending how far off it is from this one) someone should be able to provide example code.