How can I build a nested HTML list with an infinite depth from a flat array?

Question

I\'m trying to produce a multi-level HTML list from a source array that is formatted like this:

/**
 * id = unique id
 * parent_id = \"id\" that this item is         


        

Answer 1

Tested and working :)

$list = array(...);
$nested = array();

foreach ($list as $item)
{
    if ($item['parent_id'] == 0)
    {
        // Woot, easy - top level
        $nested[$item['id']] = $item;
    }
    else
    {
        // Not top level, find it's place
        process($item, $nested);
    }
}

// Recursive function
function process($item, &$arr)
{
    if (is_array($arr))
    {
        foreach ($arr as $key => $parent_item)
        {
            // Match?
            if (isset($parent_item['id']) && $parent_item['id'] == $item['parent_id'])
            {
                $arr[$key]['children'][$item['id']] = $item;
            }
            else
            {
                // Keep looking, recursively
                process($item, $arr[$key]);
            }
        }
    }
}