How to create a ul - li menu from a tree like array?

Question

I have an array with title and children index.

title is always not-null. children is an array, empty or not-empty.

Any children have title and children and so on.

$myArray = [
    0 => [
        'title'    => 'N1',
        'children' =>
            [
                0 =>
                    [
                        'title'    => 'N11',
                        'children' =>
                            [
                                0 =>
                                    [
                                        'title'    => 'N111',
                                        'children' => [],
                                    ],
                            ],
                    ],
            ],
    ],
    1 =>
        [
            'title'    => 'N2',
            'children' =>
                [
                    0 =>
                        [
                            'title'    => 'N21',
                            'children' =>
                                [],
                        ],
                ],
        ],
];

Now, I want to create a drop-down menu with this array.

I have problem with creating an unordered list (ul, li)from this array.

I want my result to be like:

<ul>
    <li>N1
        <ul>
            <li>N11
                <ul>
                    <li>N111</li>
                </ul>
            </li>
        </ul>
    </li>
    <li>N2
        <ul>
            <li>N21</li>
        </ul>
    </li>
</ul>

Answer 1

I'm sure this will work :

    function menu($arr) {
        echo "<ul>";
        foreach ($arr as $val) {

            if (!empty($val['children'])) {
                echo "<li>" . $val['title'];
                menu($val['children']);
                echo "</li>";
            } else {
                echo "<li>" . $val['title'] . "</li>";
            }
        }
        echo "</ul>";
    }

Answer 2

Suppose this is your array

$menu = array(
    array(
        'title'=>'N1',
        'children'=>array(
                'title'=>'N11',
                'children'=>array(
                        'title'=>'N111',
                        'children'=>array(),
                ),
        ),
    ),
    array(
        'title'=>'N2',
        'children'=>array(
                'title'=>'N21',
                'children'=>array(),
                )
    ),
);

You could make use of recursion to build this HTML structure.

    function createMenu($arr){
      $str = '';
      if(is_array($arr)){
             $str .= "<li>".$arr['title'];
         if(!empty($arr['children'])){
        $str .="<ul>";
        $str .= createMenu($arr['children'],$str);                   
        $str .="</ul>";
         }
         $str .= "</li>";               
      }
     return $str;  
   }

Now call the recursive function to create the HTML

$myMenu ='';
foreach($menu as $arr){
  $myMenu .= createMenu($arr);
}
echo "<ul>".$myMenu."</ul>";
exit();