WordPressで親カテゴリーを再帰的に取得

よく書く処理なので。

WP_Termオブジェクトを配列で返す場合

function find_ancestor_categories($category_id, $categories = []) {
  $category = get_category($category_id);
  $categories[] = $category;
  if($category->parent) {
    $categories = find_ancestor_categories($category->parent, $categories);
  }
  return $categories;
}

term_idを配列で返す場合

function find_ancestor_category_ids($category_id, $category_ids = []) {
  $category = get_category($category_id);
  $category_ids[] = $category->term_id;
  if($category->parent) {
    $category_ids = find_ancestor_category_ids($category->parent, $category_ids);
  }
  return $category_ids;
}