Question

I have the following array :

Array
(
    [0] => Array
        (
            [ID] => 1
            [PARENT] => 0
            [NAME] => Your first category
        )
    [1] => Array
        (
            [ID] => 2
            [PARENT] => 1
            [NAME] => Your first forum
        )
    [2] => Array
        (
            [ID] => 4
            [PARENT] => 1
            [NAME] => Another Forum
        )
    [3] => Array
        (
            [ID] => 5
            [PARENT] => 1
            [NAME] => Good Forum
        )
    [4] => Array
        (
            [ID] => 6
            [PARENT] => 0
            [NAME] => Top Forum
        )
    [5] => Array
        (
            [ID] => 7
            [PARENT] => 6
            [NAME] => Sub Forum #1
        )
    [6] => Array
        (
            [ID] => 9
            [PARENT] => 7
            [NAME] => Sub Forum #1-1
        )
    [7] => Array
        (
            [ID] => 10
            [PARENT] => 7
            [NAME] => Sub Forum #1-2
        )
    [8] => Array
        (
            [ID] => 8
            [PARENT] => 6
            [NAME] => Sub Forum #2
        )
)

OK Here I have the var_export result as requested :

array (
  0 => 
  array (
    'ID' => '1',
    'PARENT' => '0',
    'NAME' => 'Your first category',
  ),
  1 => 
  array (
    'ID' => '2',
    'PARENT' => '1',
    'NAME' => 'Your first forum',
  ),
  2 => 
  array (
    'ID' => '4',
    'PARENT' => '1',
    'NAME' => 'Another Forum',
  ),
  3 => 
  array (
    'ID' => '5',
    'PARENT' => '1',
    'NAME' => 'Good Forum',
  ),
  4 => 
  array (
    'ID' => '6',
    'PARENT' => '0',
    'NAME' => 'Top Forum',
  ),
  5 => 
  array (
    'ID' => '7',
    'PARENT' => '6',
    'NAME' => 'Sub Forum #1',
  ),
  6 => 
  array (
    'ID' => '9',
    'PARENT' => '7',
    'NAME' => 'Sub Forum #1-1',
  ),
  7 => 
  array (
    'ID' => '10',
    'PARENT' => '7',
    'NAME' => 'Sub Forum #1-2',
  ),
  8 => 
  array (
    'ID' => '8',
    'PARENT' => '6',
    'NAME' => 'Sub Forum #2',
  ),
)

Some of that arrays PARENT value corespond to another array ID value. That helps me to make them nested. But the question is: how can I create an HTML list that will look like that:

<ul>
    <li id="1">
        Your First Category
        <ul>
            <li id="2">
                Your First Forum
            </li>
            <li id="4">
                Another Forum
            </li>
            <li id="5">
                Good Forum
            </li>
        <ul>
    </li>
    <li id="6">
        Top Forum
        <ul>
            <li id="7">
                Sub Forum #1
                <ul>
                    <li id="9">
                        Sub Forum #1-1
                    </li>
                    <li id="10">
                        Sub Forum #1-2
                    </li>
                </ul>
            </li>
            <li id="7">
                Sub Forum #2
            </li>
        <ul>
    </li>
</ul>

Any idea please?

Answer 1

$new_arr = array();
foreach($arr as $data) $new_arr[$data['id']] = $data;

foreach($new_arr as $id => &$data) $data['parent'] =& $new_arr[$data['parent']];

Now you have a proper array structure.

But you may have to turn it inside out, since it’s structured by child. But your output is by parent.

So instead of the second foreach I posted, do this:

foreach($new_arr as $id => $data) $new_arr[$data['parent']]['children'][] =& $data;