pocketmine\Player::checkTeleportPosition PHP Method

    protected function checkTeleportPosition()
    {
        if ($this->teleportPosition !== null) {
            $chunkX = $this->teleportPosition->x >> 4;
            $chunkZ = $this->teleportPosition->z >> 4;
            for ($X = -1; $X <= 1; ++$X) {
                for ($Z = -1; $Z <= 1; ++$Z) {
                    if (!isset($this->usedChunks[$index = Level::chunkHash($chunkX + $X, $chunkZ + $Z)]) or $this->usedChunks[$index] === false) {
                        return false;
                    }
                }
            }
            $this->sendPosition($this, null, null, 1);
            $this->spawnToAll();
            $this->forceMovement = $this->teleportPosition;
            $this->teleportPosition = null;
            return true;
        }
        return true;
    }