Converts a flat array to a tree structure with references

flatArrayToTree.php

<?php

/**
 * @param array $navigation
 * @return array
 */
private function flatArrayToTree(array $navigation): array
{
    $navigationTree = [];

    foreach ($navigation as $nav) {
        $navigationTree[$nav['id']] = $nav;
    }

    foreach ($navigationTree as &$nav) {
        if (false === isset($nav['children'])) {
            $nav['children'] = [];
        }

        // Do not add root node
        if (null === $nav['parentId'] || false === isset($navigationTree[$nav['parentId']])) {
            continue;
        }

        if (false === array_key_exists('children', $navigationTree[$nav['parentId']])) {
            $navigationTree[$nav['parentId']]['children'] = [];
        }
        $navigationTree[$nav['parentId']]['children'][$nav['url']] = &$nav;
    }

    return $navigationTree;
}