Термины в виде дерева иерархии

Функция для получения терминов таксономии в виде иерархии:

function taxonomy_get_nested_tree($terms = array(), $max_depth = NULL, $parent = 0, $parents_index = array(), $depth = 0) {
    if (is_int($terms)) {
        $terms = taxonomy_get_tree($terms);
    }

    foreach($terms as $term) {
        foreach($term->parents as $term_parent) {
            if ($term_parent == $parent) {
                $return[$term->tid] = $term;
            }
            else {
                $parents_index[$term_parent][$term->tid] = $term;
            }
        }
    }

    foreach($return as &$term) {
        if (isset($parents_index[$term->tid]) && (is_null($max_depth) || $depth < $max_depth)) {
            $term->children = taxonomy_get_nested_tree($parents_index[$term->tid], $max_depth, $term->tid, $parents_index, $depth + 1);
        }
    }

    return $return;
}

Функция для вывода терминов в виде списка:

function output_taxonomy_nested_tree($tree) {
    if (count($tree)) {
        $output = '<ul class="taxonomy-tree">';
        foreach ($tree as $term) {
            $output .= '<li class="taxonomy-term">';
            $output .= $term->name;
            if (!empty($term->children)) {
                $output .= output_taxonomy_nested_tree($term->children);
            }
            $output .= '</li>';
        }
        $output .= '</ul>';
    }
    return $output;
}

Простая функция для получения вложенного массива из taxonomy_get_tree().

function simple_taxonomy_tree($vid, $parent = 0) {
  $items = array();
  $terms = taxonomy_get_tree($vid);

  foreach ($terms as $term) {
    if (in_array($parent, $term->parents)) {
      $items[$term->tid] = array(
        'data' => $term->name,
        'tid' => $term->tid,
        'children' => _mymodule_taxonomy_tree($terms, $term->tid),
      );
    }
  }

  return $items;
}