Setting armor without knowing the type.

setHelmet, setBoots blah... I want to know a way to just simply set the armor without needing to determine the type of armor it is. Not add it into the inv, but SET it.

PHP:

$inv->setArmorItem(($item->getId() - 2) % 4, $item);

(This requires determining the type too, but in a simple way)

Explain?

All helmet item IDs are 4n+2, chestplates 4n+3, vice versa