NBT CompoundTag to JSON in PocketMine-MP using a stack for iterative node traversal

nbt-json.php

<?php

declare(strict_types=1);

use pocketmine\nbt\tag\CompoundTag;
use pocketmine\player\Player;
use pocketmine\Server;

$server = Server::getInstance();
assert(isset($sender) && $sender instanceof Player);

if(!($sender instanceof Player)){
	return;
}

$nbtToJson = static function(CompoundTag $nbt) : array{
	$data = $nbt->getValue();
	$stack = [];
	foreach($data as &$v){
		$stack[] = &$v;
	}
	unset($v);
	while(($index = array_key_last($stack)) !== null){
		$v = &$stack[$index];
		unset($stack[$index]);
		$v = $v->getValue();
		if(is_array($v)){
			foreach($v as &$vv){
				$stack[] = &$vv;
			}
			unset($vv);
		}
	}
	return $data;
};

$item = $sender->getInventory()->getItemInHand();
$nbt = $item->getNamedTag();
$data = $nbtToJson($nbt);
echo json_encode($data, JSON_THROW_ON_ERROR | JSON_PRETTY_PRINT);