pocketmine\level\Level::unloadChunks PHP Method

    public function unloadChunks(bool $force = false)
    {
        if (count($this->unloadQueue) > 0) {
            $maxUnload = 96;
            $now = microtime(true);
            foreach ($this->unloadQueue as $index => $time) {
                Level::getXZ($index, $X, $Z);
                if (!$force) {
                    if ($maxUnload <= 0) {
                        break;
                    } elseif ($time > $now - 30) {
                        continue;
                    }
                }
                //If the chunk can't be unloaded, it stays on the queue
                if ($this->unloadChunk($X, $Z, true)) {
                    unset($this->unloadQueue[$index]);
                    --$maxUnload;
                }
            }
        }
    }