<?php


function set_nested_array_value(&$array, $path, &$value, $delimiter = '/')
{
    $pathParts = explode($delimiter, $path);
    //print_r
    $current = &$array;
    foreach ($pathParts as $key) {
        $current = &$current[$key];
    }

    $backup = $current;
    $current = $value;

    return $backup;
}

function pruneTree($array)
{
    $result = [];
    $i = 0;

    foreach ($array as $key => $node) {
        $r = [];
        // set the slug if it exists
        if (isset($node['folder'])) {
            $r['slug'] = $node['folder'];
            unset($node['folder']);
        }
        $r['text'] = $key;
        // set the children through recursion
        $r['children'] = pruneTree($node);

        // when the node does not have slug (ie: DOCUMENTS)
        // set the slug of the first child - to match expected results.
        if (!isset($r['slug']) && isset($r['children'][0])) {
            $r['slug'] = $r['children'][0]->slug;
        }
        // transform to object - to match expected results.
        $result[$i] = (object) $r;
        $i++;
    }

    return $result;
}

function buildTree($results)
{
    $data = [];
    foreach ($results as $path) {

        $r = [];
        $v = ['folder' => $path['folder']];
        $res = set_nested_array_value($r, $path['path_string'], $v);
        $data = array_merge_recursive($data, $r);
    }
    return $data;
}

$dsn = 'mysql:dbname=stackoverflow;host=127.0.0.1';
$user = 'rootornoroot';
$password = '******';
$db = new PDO($dsn, $user, $password);

$query = "SELECT * FROM validation_paths";

$results = $db->query($query);

$r = [
    'children' => pruneTree(buildTree($results))
    ];
print_r((object) $r);