Wordpress Insert Post Terms

gistfile1.txt

/**
 * Insert post terms
 *
 * @param array|string $terms
 * @param integer $post_id
 * @return void
 */
function _insertPostTerms($terms, $post_id, $taxonomy)
{
  $term_ids = [];

  foreach ((array) $terms as $term)
  {
    $term_id = term_exists($term, $taxonomy);

    if(!$term_id)
    {
      $term_id = wp_insert_term($term, $taxonomy);
    }

    $term_ids[] = (int) $term_id['term_id'];
  }

  wp_set_post_terms($post_id, $term_ids, $taxonomy);
}

Remember to only interact with Taxonomies after the taxonomy has been registered, in most cases in the init action.