如何从get_categories

$categories = get_categories();

// First index all categories by parent id, for easy lookup later
$cats_by_parent = array();
foreach ($categories as $cat)
{
  $parent_id = $cat->category_parent;
  if (!array_key_exists($parent_id, $cats_by_parent)) 
  {
    $cats_by_parent[$parent_id] = array();
  }
  $cats_by_parent[$parent_id][] = $cat;
}

// Then build a hierarchical tree
$cat_tree = array();
function add_cats_to_bag(&$child_bag, &$children)
{
   global $cats_by_parent;
   foreach ($children as $child_cat) 
   {
     $child_id = $child_cat->cat_ID;
     if (array_key_exists($child_id, $cats_by_parent)) 
     {
        $child_cat->children = array();
        add_cats_to_bag($child_cat->children, $cats_by_parent[$child_id]);
     }
     $child_bag[$child_id] = $child_cat;
   }
}
add_cats_to_bag($cat_tree, $cats_by_parent[0]);