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

Print:

function printListRecursive(&$list,$parent=0){
    $foundSome = false;
    for( $i=0,$c=count($list);$i<$c;$i++ ){
        if( $list[$i]['parent_id']==$parent ){
            if( $foundSome==false ){
                echo '<ul>';
                $foundSome = true;
            }
            echo '<li>'.$list[$i]['text'].'</li>';
            printListRecursive($list,$list[$i]['id']);
        }
    }
    if( $foundSome ){
        echo '</ul>';
    }
}

printListRecursive($list);

Create multidimensional array:

function makeListRecursive(&$list,$parent=0){
    $result = array();
    for( $i=0,$c=count($list);$i<$c;$i++ ){
        if( $list[$i]['parent_id']==$parent ){
            $list[$i]['childs'] = makeListRecursive($list,$list[$i]['id']);
            $result[] = $list[$i];
        }
    }
    return $result;
}

$result = array();
$result = makeListRecursive($list);
echo '<pre>';
var_dump($result);
echo '</pre>';

Answer 2

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]);
            }
        }
    }
}

Answer 3

Some methods I recently wrote, maybe some will help, sorry I'm short on time and cannot rewite them to match your needs.

This code is actually a part of Kohana Framework Model, method ->as_array() is used to flat an Database_Result object.

function array_tree($all_nodes){
    $tree = array();
    foreach($all_nodes as $node){
        $tree[$node->id]['fields'] = $node->as_array();
        $tree[$node->id]['children'] = array();

        if($node->parent_id){
             $tree[$node->parent_id]['children'][$node->id] =& $tree[$node->id];
        }
    }


    $return_tree = array();
    foreach($tree as $node){
        if($node['fields']['depth'] == 0){
            $return_tree[$node['fields']['id']] = $node;
        }
    }

    return $return_tree;
}

array_tree() is used to make a tree out of a flat array. The key feature is the =& part ;)

function html_tree($tree_array = null){
        if( ! $tree_array){
           $tree_array = $this -> array_tree();
        }

        $html_tree = '<ul>'."\n";
        foreach($tree_array as $node){
            $html_tree .= $this->html_tree_crawl($node);
        }
        $html_tree .= '</ul>'."\n";


        return $html_tree;
    }

function html_tree_crawl($node){
        $children = null;

        if(count($node['children']) > 0){
            $children = '<ul>'."\n";
            foreach($node['children'] as $chnode){
                $children .= $this->html_tree_crawl($chnode);
            }
            $children .= '</ul>'."\n";
        }

        return $this->html_tree_node($node, $children);
    }

html_tree_node() is a simple method to display current node and children in HTML. Example below:

<li id="node-<?= $node['id'] ?>">
    <a href="#"><?= $node['title'] ?></a>
    <?= (isset($children) && $children != null) ? $children : '' ?>
</li>