FRONTEND_MVC/helpers/Tree.php

<?php
namespace app\helpers;

use yii\helpers\ArrayHelper;

class Tree
{
	public static function buildTree(array $elements, $parentId = 0) {
		$branch = array();
		foreach ($elements as $element) {
			if ($element['parent_id'] == $parentId) {
				$children =self::buildTree($elements, $element['id']);
				if ($children) {
					$element['children'] = $children;
				}
				$branch[] = $element;
			}
		}
		return $branch;
	}

	public static function drawTree( $items, $draw, $lavel = 0 ){
		foreach( $items as $item ){
			echo $draw->render('_item', [
			'model' => $item['item'], 'lavel' => $lavel
			]);
			if( isset( $item['children'] ) && $item['children'] ){
				self::drawTree( $item['children'], $draw, $lavel+1 );
			}
		}
	}

}