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

What function(s) can be found in the Wordpress world make it possible for a wordpress plugin developer to:

  1. Look for the presence of a category
  2. Produce a new category
  3. Assign a publish to some category

how about these:

  1. To ascertain if a category is available on the given publish, use get_the_category($id) and appearance what it really returns. To ascertain if a category is available whatsoever, use is_category( $category )
  2. use wp_create_category( $title, $parent )
  3. use wp_set_object_terms( $object_id, $terms, $taxonomy, $append )