public function getAdditionalData(\Magento\Quote\Model\Quote\Item $quoteItem) { $additionalData = $this->proxyItem->getAdditionalData(); $existAdditionalData = $quoteItem->getAdditionalData(); $existAdditionalData = is_string($existAdditionalData) ? @unserialize($existAdditionalData) : []; return serialize(array_merge((array) $existAdditionalData, $additionalData)); }