Give items doesn't work

I give a player items, when he killed someone. But only he item in the killers hand doesn't update. Does someone know why?
My code:

PHP:

$killer->getInventory()->setItem(0, $item);
$killer->getInventory()->setItem(1, $item);

 

Send the full code.

 

Do I need to send something to update the item in the killers hand?

PHP:

$killer->getInventory()->clearAll();
$item = Item::get(271, 0, 1);
$killer->getInventory()->setItem(0, $item); 
$killer->getInventory()->setItem(1, $item);

 

If you want to, you can do that, tho your code must automatically do it.

PHP:

$player->getInventory()->sendSlot($slotnumber, $player);


Where $slotnumber is the slot number.