PHP Generate UL LI , UL LI

Can't figure out how-to generate this menu using a while-loop. This is an example of my code:

• Hoofdmenu 1
  { $menuArray[$type]['title'] = $title; } else // else, it's a child, so append it to the parent { $menuArray[$type]['subitems'][] = $title; }

  Then, having $menuArray, loop through it to create the menu:

  ?><ul id="nav"><?php
  foreach ($menuArray as $item)
  {
      ?><li><a href="#">$item['title']</a><?php
      ?><ul class="sub"><?php
  
      foreach ($item['subitems'] as $subItem)
      {
          <li><a href="#">$subItem</a></li>
      }
  
      ?></ul><?php
      ?></li><?php
  }
  ?></ul><?php
  

Solution 2:

function load()
{
    global $conn;


    $query = "SELECT *  FROM sub_category WHERE main_category_id='1'";
    $result = mysqli_query($conn,$query);
    while($row = mysqli_fetch_assoc($result)){
        $cat_id=$row['sub_category_id'];

    echo '<li><a href="?id='.$row['sub_category_id'].'">'.$row['sub_category_name'].'</a>';

    $query2 = "SELECT *  FROM categories WHERE sub_category_id='$cat_id'";
    $result2 = mysqli_query($conn,$query2);    
    echo '<ul class="sub">';
    while($row2 = mysqli_fetch_assoc($result2))
    {   
        echo '<li><a href="?id='.$row2['category_id'].'">'.$row2['category_name'].'</a></li>';


    }
        echo '</ul>';
    echo '</li>';}


}

Solution 3:

in this example parent_id column used and ul-li list build with references- it makes only 1 sql query and use recoursion for rendering output, this code can be simply changed for your needs

        <?php
 /**
  * Module for displaying data from items table
  */
class App_Modules_Tree  extends   App_AbstractModule {

    /**
        * array for storing data
        *
        * @var array
        */
    private $tree = array();
       /**
        * html - output of current module
        *
        * @var string
        */
        private $output = ''; 

      /**
       * Retreives data from table items.
       *
       * @return void
       */
        private function _getData()
    {
        $pdo = App_Registry::get('pdo');
        $levels = array();
        foreach ($pdo->query('SELECT * FROM items ORDER BY parent_id ASC',PDO::FETCH_OBJ) as $k=>$v){
                   // references
             $current =  &$levels[ $v->id ] ;
                 $current['parent_id'] = $v->parent_id;
                 $current['name'] = $v->name;
                 if (0 == $v->parent_id){
                 $this->tree[ $v->id ] = &$current;
                 } else {
             $levels[$v->parent_id ]['children'][$v->id] = &$current;
                 }
        }
    }   

    /*
    *App_AbstractModule::preRender overriding
        * @return void
    */
    protected  function preRender()
    {
        $this->_getData();
        }
      /**
       * recursively build html output.
       *
       * @return string
       */
    private function _render($arr)
    {
        $this->output.= '<ul>';
        foreach ($arr as $k=>$v)
        {
            $this->output.= '<li>'.$v['name'].'</li>';
            if( !empty($v['children'])){
                $this->_render($v['children']);
            }
        }
        $this->output.= '</ul>';
        return $this->output;
    }
    /*
    *App_AbstractModule::render overriding
        * @return string
    */
    protected  function render()
    {
            return $this->_render($this->tree);
    }

}