Solved Switching Items in players inventory

Does anyone have a basic analogy on how to switch players items in there inventory?
(The item in hand with a random one in the inventory)
Everything I have been trying is duping the items.

 

PHP:

/** @var Player $player */
$inv = $player->getInventory();

$rand = mt_rand(0, $inv->getSize());
$item1 = $inv->getItem($rand);
$item2 = $inv->getItemInHand();

$inv->setItem($rand, $item2);
$inv->setItemInHand($item1));