[Mediawiki-l] getParentCategoryTree()

I am trying to find the most efficient way to get a list of all the categories that make up the category tree for an article. So if an article belongs to Category x and Category x belongs to Category y and z , i want to get the list: x, y, z

I assumed that getParentCategoryTree() would do just that ... But it is only returning a title's parent categories not the entire category tree. So in the above case it is only returning 'x' instead of x, y, z.

I am using the following:

$CategoryTree = $wgTitle->getParentCategoryTree(); foreach ($CategoryTree as $key => $value){ $nt = Title::newFromText($key); $category list .= $nt->getText(); }

Am I misunderstanding the purpose of getParentCategoryTree() ? If so, is there another way of getting the list of categories i am looking for?

Thanks in advance for any help you can give