How to display a mega menu using nested sets?

Question

PHP

There is a table in the database: id, name, left_key, right_key, level.
And so the tree. I pull out an array of objects with a request, but I can’t integrate it into the layout . The layout looks like this:SELECT * FROM my_tree ORDER BY left_key ASC

<div id="main-menu" class="col-sm-9 main-menu">
                    <nav class="navbar navbar-default">
                        <div class="container-fluid">
                            <div class="navbar-header">
                                <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar" aria-expanded="false" aria-controls="navbar">
                                    <i class="fa fa-bars"></i>
                                </button>
                                <a class="navbar-brand" href="#">MENU</a>
                            </div>
                            <div id="navbar" class="navbar-collapse collapse">
                                <ul class="nav navbar-nav">
              
        
                                    <li class="dropdown">
                                        <a href="category.html" class="dropdown-toggle" data-toggle="dropdown"></a>
                                        <ul class="dropdown-menu mega_dropdown" role="menu" style="width: 830px;">
                                            <li class="block-container col-sm-3">
                                                <ul class="block">
                                                    <li class="img_container">
                                                        <a href="#">
                                                            <img class="img-responsive" src="themes/KSHOP/data/men.png" alt="sport">
                                                        </a>
                                                    </li>
                                                   <li class="link_container group_header">
                                                        <a href="#"></a>
                                                    </li>
                                                    <li class="link_container"><a href="#"></a></li>
 												</ul>
                                            </li> 
                                        </ul>
                                    </li>
                                </ul>
                            </div><!--/.nav-collapse -->
                        </div>
                    </nav>
                </div>

Maybe someone can tell me how to do it correctly, in my case