pocketmine\utils\VectorIterator::valid PHP Метод

    public function valid()
    {
        $this->scan();
        return $this->currentBlock !== -1;
    }

 private function getAvailableBlockSpace(ChunkManager $level, Vector3 $from, Vector3 $to)
 {
     $count = 0;
     $iter = new VectorIterator($level, $from, $to);
     while ($iter->valid()) {
         $iter->next();
         $pos = $iter->current();
         if (!isset($this->overridable[$level->getBlockIdAt($pos->x, $pos->y, $pos->z)])) {
             return $count;
         }
         $count++;
     }
     return -1;
 }