pocketmine\Player::unloadChunk PHP Method

    private function unloadChunk($x, $z, Level $level = null)
    {
        $level = $level === null ? $this->level : $level;
        $index = Level::chunkHash($x, $z);
        if (isset($this->usedChunks[$index])) {
            foreach ($level->getChunkEntities($x, $z) as $entity) {
                if ($entity !== $this) {
                    $entity->despawnFrom($this);
                }
            }
            unset($this->usedChunks[$index]);
        }
        $level->unregisterChunkLoader($this, $x, $z);
        unset($this->loadQueue[$index]);
    }