pocketmine\tile\Chest::checkPairing PHP Method

    protected function checkPairing()
    {
        if (($pair = $this->getPair()) instanceof Chest) {
            if (!$pair->isPaired()) {
                $pair->createPair($this);
                $pair->checkPairing();
            }
            if ($this->doubleInventory === null) {
                if (($p = $pair->getDoubleInventory()) instanceof DoubleChestInventory) {
                    $this->doubleInventory = $p;
                } else {
                    if ($pair->x + ($pair->z << 15) > $this->x + ($this->z << 15)) {
                        //Order them correctly
                        $this->doubleInventory = new DoubleChestInventory($pair, $this);
                    } else {
                        $this->doubleInventory = new DoubleChestInventory($this, $pair);
                    }
                }
            }
        } else {
            $this->doubleInventory = null;
            unset($this->namedtag->pairx, $this->namedtag->pairz);
        }
    }