Функция собирающие все дерево из представленного списка:

function get_cat_tree($rows,$lvlstr,$parentid,$prodmass)
 {
 $ret='';$show=0;if (!isset($childmass)) $childmass=array();
 foreach($rows as $item_op) 
 {
 if ($item_op->category_parent_id==$parentid)
 { 
 $ret.='
 <div class="vmcatname vmcatname_'.$item_op->virtuemart_category_id.' dsn" onclick="jQuery('."'.tovmas'".').hide();jQuery('."'.tovmas_".$item_op->virtuemart_category_id."'".').show();">';
 if (isset($prodmass[$item_op->virtuemart_category_id]) and count($prodmass[$item_op->virtuemart_category_id])>0) $ret.='<span class="updwar icon-arrow-down-3">&nbsp;</span>';
 $ret.='<h4>('.$item_op->virtuemart_category_id.')'.$lvlstr.$item_op->name;
 if (isset($prodmass[$item_op->virtuemart_category_id]) and count($prodmass[$item_op->virtuemart_category_id])>0) 
 $ret.='<span class="reddiv_ reddiv_'.$item_op->virtuemart_category_id.'"> ('.count($prodmass[$item_op->virtuemart_category_id]).')</span>';
 $ret.='</h4>
 </div>';
 $retmass=get_cat_tree($rows,$lvlstr.'&nbsp;-&nbsp;',$item_op->virtuemart_category_id,$prodmass);
 $ret.=$retmass['str'];
 
 if (isset($retmass['chlidmass']) and count($retmass['chlidmass'])>0) $childmass=array_merge($childmass, $retmass['chlidmass']);
 //дочерняя ветка имеет товары
 if ($retmass['show']==1) 
 {
 $show=1;
 //$ret.='<div>['.$item_op->virtuemart_category_id.'] has - child</div>';
 $childmass[]=$item_op->virtuemart_category_id;
 if ($item_op->category_parent_id>0) $childmass[]=$item_op->category_parent_id;
 }
 //блок товаров
 if (isset($prodmass[$item_op->virtuemart_category_id]) and count($prodmass[$item_op->virtuemart_category_id])>0) 
 {
 $ret.='<div style="display:none" class="tovmas tovmas_'.$item_op->virtuemart_category_id.'"><ul class="tovmassul">';
 foreach($prodmass[$item_op->virtuemart_category_id] as $item) $ret.= $item;
 $ret.='</ul></div>';
 $show=1;$childmass[]=$item_op->virtuemart_category_id;
 if ($item_op->category_parent_id>0) $childmass[]=$item_op->category_parent_id;
 } 
 }
 }
 $childmass=array_unique($childmass);
 return array('str'=>$ret,'show'=>$show,'chlidmass'=>$childmass);
 }

Вызов:

$db = JFactory::getDbo();
 $db->setQuery(" select v.virtuemart_category_id,v.category_parent_id,
 (select category_name from #__virtuemart_categories_ru_ru vv where vv.virtuemart_category_id=v.virtuemart_category_id) as name 
 from #__virtuemart_categories v order by name
 ");$cat_lists = $db->loadObjectList();
.....
if (count($cat_lists)>0) 
 {
 $tree=get_cat_tree($cat_lists,'',0,$prodmass);
 $txt=$tree['str'];
 foreach($tree['chlidmass'] as $item) $txt=str_replace('vmcatname_'.$item.' dsn','vmcatname_'.$item.'',$txt);
 echo $txt;
 }

В данном примере мы прячем ветки, без товаров через css.