How to use...

How to use

PHP:

setContents()

with chest and

PHP:

onSlotChange()

with chest?

onSlotChange() is an internal function. You should not use it.

Use addItem() to add items, and remove(), and setSlot().

How to get chest if event is PlayerInteractEvent (internal function onPlayerInteract())

PHP:

use pocketmine\tile\Chest;

$chest = $event->getBlock()->getLevel()->getTile($event->getBlock());
if($chest instanceof Chest){
  // execute logic here
}