nestedSets getTree

func.php

<?php 

public function getTree(): array
{
    $trees = [];
    $stack = [];

    $categories = ...;

    foreach ($categories as $category) {
        $count = count($stack);

        $item = $category;
        $item['childs'] = [];

        while ($count > 0 && $stack[$count - 1]['depth'] >= $item['depth']) {
            array_pop($stack);
            $count--;
        }

        if ($count === 0) {
            $trees[$category['id']] = $item;
            $stack[] = &$trees[$category['id']];
        } else {
            $stack[$count - 1]['childs'][$category['id']] = $item;
            $stack[] = &$stack[$count - 1]['childs'][$category['id']];
        }
    }

    return $trees;
}