<?php

$progCat = new Category();
$progCat->setName('Programming');

$phpCat = new Category();
$phpCat->setName('PHP');

$javaCat = new Category();
$javaCat->setName('Java');

$netCat = new Category();
$netCat->setName('.NET');


$em->beginTransaction();

$hm = new HierarchicalManager($em);

$item = $progCat || $hm->getNode($progCat); // ???
$rootNode = $hm->createRoot($item);

$rootNode->addChild($hm->getNode($phpCat));
$rootNode->addChild($hm->getNode($javaCat));
$rootNode->addChild($hm->getNode($netCat));

$em->flush();
$em->clear();

$em->commit();