Online PHP editor | output for qOvd0

<?php $arr = array( [ "name" => "cat1", "id" => "1", "parent" => "", ], [ "name" => "cat2", "id" => "2", "parent" => "", ], [ "name" => "subcat1", "id" => "6", "parent" => "1", ], [ "name" => "subsubcat1", "id" => "7", "parent" => "6", ], [ "name" => "subcat2", "id" => "5", "parent" => "2", ], ); function list_item($arr, $item) { echo "<li>{$item['name']}</li>\n"; // find any children $children = array_filter($arr, function ($i) use ($item) { return $i['parent'] == $item['id']; }); if (!empty($children)) { echo "<ul>\n"; foreach ($children as $child) { list_item($arr, $child); } echo "</ul>\n"; } } $parents = array_filter($arr, function ($item) { return !$item['parent'];}); echo "<ul>\n"; foreach ($parents as $parent) { list_item($arr, $parent); } echo "</ul>\n";