Question

This is a followup to my question about programmatically adding wordpress categories based on post content.

What function(s) are available in the WordPress universe to enable a plugin developer to:

1. Check for the existence of a category
2. Create a new category
3. Assign a post to a category

Answer 1

what about these:

1. To see if a category exists on a given post, use get_the_category($id) and check what it returns. To see if a category exists at all, use is_category( $category )
2. use wp_create_category( $name, $parent )
3. use wp_set_object_terms( $object_id, $terms, $taxonomy, $append )