Proper way to print root menu items and child menu items in separated div's.

menu_data_raw.php

<?php

$menu = array(
    0 => array('display' => 'Writers', 'url' => 'http://www.famousauthors.org/', 'sub' => array(
        array('display' => ' Alan Moore', 'url' =>'http://www.famousauthors.org/alan-moore'),
        array('display' => ' Dan Brown', 'url' =>'http://www.famousauthors.org/dan-brown'),
        array('display' => ' Mario Puzo', 'url' =>'http://www.famousauthors.org/mario-puzo'),
    )),
    1 => array('display' => 'Musicians', 'url' => 'http://www.thefamouspeople.com/musicians.php', 'sub' => array(
        array('display' => ' Composer', 'sub' => array(
            array('display' => 'Cesar Franck ', 'url' =>'http://www.thefamouspeople.com/profiles/cesar-franck-403.php'),
            array('display' => 'Clara Wieck Schumann', 'url' =>'http://www.thefamouspeople.com/profiles/clara-wieck-schumann-393.php'),
        )),
        array('display' => 'Singers', 'sub' => array(
            array('display' => 'Pop Music', 'sub' => array(
                array('display' => 'Beyonce Knowles', 'url' =>'http://top40.about.com/od/artistsac/p/beyonce.htm'),
                array('display' => 'Robbie Williams', 'url' =>'http://top40.about.com/od/artistsls/p/robbiewilliams.htm'),
            )),
            array('display' => 'Rock Music', 'sub' => array(
                array('display' => 'Axle Rose', 'url' =>'http://www.mademan.com/mm/10-most-famous-rock-musicians-ever.html#vply=0'),
                array('display' => 'Ozzy Osborne', 'url' =>'http://www.mademan.com/mm/10-most-famous-rock-musicians-ever.html#vply=0'),
            )),
        )),
    )),
    2 => array('display' => 'Contact Us', '#contact'),
);

menu_view.php

<?php

class MenuView
{
    /**
     * Get Just Main Categories
     * @param $menu
     * @return string
     */
    static public function getMainCategories($menu)
    {
        $html = "\n\t".'<ul>';
        foreach ($menu as $menuRow)
        {
            $html .= self::getMenuItem($menuRow);
        }
        $html .= "\n\t".'</ul>'."\n";
        return $html;
    }

    /**
     * Get Main Categories Item
     * @param $item
     * @return string
     */
    static public function getMenuItem($item)
    {
        $html = "\n\t".'<li> ';

        if (isset($item['url'])) $html .= '<a href="'.$item['url'].'">';
        $html .= $item['display'];
        if (isset($item['url'])) $html .= '</a>';
        $html .= '</li>'."\n";

        return $html;
    }

    /**
     * Check has menu item it's Child Menu
     * @param $menuItem
     * @return bool
     */
    static public function hasChild($menuItem)
    {
        return isset($menuItem['sub']);
    }

    /**
     * Get Separated Menu Item For Submenu
     * @param $menu
     * @param int $level
     * @return string
     */
    static public function getSubMenu($menu, $level = 1)
    {
        $printMenu = self::isFirstSubmenuLevel($level) ? "\n\t".'<ul class="submenu">' : "\n\t".'<ul>';
        foreach ($menu as $menu_item)
        {
            $printMenu .= "\n\t".'<li>';
            if (isset($menu_item['url'])) $printMenu .= '<a href="'.$menu_item['url'].'">';
            $printMenu .= $menu_item['display'];
            if (isset($menu_item['url'])) $printMenu .= '</a>';
            if (isset($menu_item['sub']))
            {
                $printMenu .= self::getSubMenu($menu_item['sub'], $level + 1);

            }
            $printMenu .= '</li>'."\n";

        }
        $printMenu .= '</ul>'."\n";

        return $printMenu;
    }

    /**
     * Is level appropriate for first sub-menu level
     * @param $level
     *
     * @return bool
     */
    static private function isFirstSubmenuLevel($level)
    {
        return $level <= 1;
    }


}

output.html

<div id="mainCategories">
    
	<ul>
	<li> <a href="http://www.famousauthors.org/">Writers</a></li>

	<li> <a href="http://www.thefamouspeople.com/musicians.php">Musicians</a></li>

	<li> Contact Us</li>

	</ul>
</div>
<div id="subMenus">
                
	<ul class="submenu">
	<li><a href="http://www.famousauthors.org/alan-moore"> Alan Moore</a></li>

	<li><a href="http://www.famousauthors.org/dan-brown"> Dan Brown</a></li>

	<li><a href="http://www.famousauthors.org/mario-puzo"> Mario Puzo</a></li>
</ul>
                    
	<ul class="submenu">
	<li> Composer
	<ul>
	<li><a href="http://www.thefamouspeople.com/profiles/cesar-franck-403.php">Cesar Franck </a></li>

	<li><a href="http://www.thefamouspeople.com/profiles/clara-wieck-schumann-393.php">Clara Wieck Schumann</a></li>
</ul>
</li>

	<li>Singers
	<ul>
	<li>Pop Music
	<ul>
	<li><a href="http://top40.about.com/od/artistsac/p/beyonce.htm">Beyonce Knowles</a></li>

	<li><a href="http://top40.about.com/od/artistsls/p/robbiewilliams.htm">Robbie Williams</a></li>
</ul>
</li>

	<li>Rock Music
	<ul>
	<li><a href="http://www.mademan.com/mm/10-most-famous-rock-musicians-ever.html#vply=0">Axle Rose</a></li>

	<li><a href="http://www.mademan.com/mm/10-most-famous-rock-musicians-ever.html#vply=0">Ozzy Osborne</a></li>
</ul>
</li>
</ul>
</li>
</ul>
        </div>

view.php

<div id="mainCategories">
    <?= MenuView::getMainCategories($menu);?>
</div>
<div id="subMenus">
<?php foreach ($menu as $item) : ?>
    <?php if (MenuView::hasChild($item)): ?>
            <?= MenuView::getSubMenu($item['sub']) ?>
    <?php endif ?>
<?php endforeach; ?>
</div>