How to draw a multi-level menu with an array sorted by the left key nested sets?

Question

PHP

There is a table nested sets (id, name, lef_key, right_key, level), I pull out a tree from the database with a query: Then I form an array of objects in a loop:'SELECT * FROM my_tree ORDER BY left_key'

while($row=$sth->fetchObject()){
      $tree[]=$row;
    }

How do I draw a multi-level menu through ul and li.
I've searched a lot of articles on Google, but I haven't found any useful information. Maybe there is some ready-made solution, or for this it is better to use something else, not nested sets, or there is an article describing such an implementation. Thanks in advance.