This question has been answered by m.engel. See the first response.
// a simple example how an 404 routing is done
$catAlias = substr($_GET['q'], 0, strrpos($_GET['q'], '/') + 1);
if ($categoryId = $modx->findResource($catAlias)) {
$_GET['article'] = substr(basename($_GET['q']), 0, -5);
$modx->sendForward($categoryId);
}
$modx->sendForward(234);
Try the CustomRequest extra for this: http://jako.github.io/CustomRequest/usage/Thank you for answering
[[~14]]product/[[+product_id]]/[[+url_thing]].html