Magenton 2 observer unable to serialize value

Question

Hi am getting unable to serialize value error in log files

below are my 2 observers

<?php
namespace Mageplaza\HelloWorld\Observer;
use Magento\Framework\Event\Observer as EventObserver;
use Magento\Framework\Event\ObserverInterface;
class CheckoutCartProductAddAfterObserver implements ObserverInterface
{
   
    protected $_layout;
    protected $_storeManager;
    protected $_request;
    
    public function __construct(
        \Magento\Store\Model\StoreManagerInterface $storeManager,
        \Magento\Framework\View\LayoutInterface $layout,
        \Magento\Framework\App\RequestInterface $request
    )
    {
        $this->_layout = $layout;
        $this->_storeManager = $storeManager;
        $this->_request = $request;
    }
 
    public function execute(EventObserver $observer)
    {
     
        $item = $observer->getQuoteItem();
        $additionalOptions = array();
        if ($additionalOption = $item->getOptionByCode('additional_options')){
            $additionalOptions = (array) unserialize($additionalOption->getValue());
        }
        $post = $this->_request->getParam('checkout_cart_add');
        if(is_array($post))
        {
            foreach($post as $key => $value)
            {
                if($key == '' || $value == '')
                {
                    continue;
                }
                $additionalOptions[] = [
                    'label' => $key,
                    'value' => $value
                ];
            }
        }
        if(count($additionalOptions) > 0)
        {
            $item->addOption(array(
                'code' => 'additional_options',
                'value' => serialize($additionalOptions)
            ));

             $observer->getProduct()->addCustomOption('additional_options', serialize($additionalOptions));
        }

    }
}

2nd

<?php
namespace Mageplaza\HelloWorld\Observer;
use Magento\Framework\Event\Observer as EventObserver;
use Magento\Framework\Event\ObserverInterface;

class SalesModelServiceQuoteSubmitBeforeObserver implements ObserverInterface
{
    private $quoteItems = [];
    private $quote = null;
    private $order = null;
   
    public function execute(EventObserver $observer)
    {
        $this->quote = $observer->getQuote();
        $this->order = $observer->getOrder();
        foreach($this->order->getItems() as $orderItem)
        {
            if(!$orderItem->getParentItemId() && $orderItem->getProductType() == \Magento\Catalog\Model\Product\Type::TYPE_SIMPLE)
            {
                if($quoteItem = $this->getQuoteItemById($orderItem->getQuoteItemId())){
                    if ($additionalOptionsQuote = $quoteItem->getOptionByCode('additional_options'))
                    {
                       
                        if($additionalOptionsOrder = $orderItem->getProductOptionByCode('additional_options'))
                        {
                            $additionalOptions = array_merge($additionalOptionsQuote, $additionalOptionsOrder);
                        }
                        else
                        {
                            $additionalOptions = $additionalOptionsQuote;
                        }
                        if(count($additionalOptions) > 0)
                        {
                            $options = $orderItem->getProductOptions();
                            $options['additional_options'] = unserialize($additionalOptions->getValue());
                            $orderItem->setProductOptions($options);
                        }
                    }
                }
            }
        }
    }
    private function getQuoteItemById($id)
    {
        if(empty($this->quoteItems))
        {
          
            foreach($this->quote->getItems() as $item)
            {
                
                if(!$item->getParentItemId() && $item->getProductType() == \Magento\Catalog\Model\Product\Type::TYPE_SIMPLE)
                {
                    $this->quoteItems[$item->getId()] = $item;
                }
            }
        }
        if(array_key_exists($id, $this->quoteItems))
        {
            return $this->quoteItems[$id];
        }
        return null;
    }
}

any fix for this

error which am getting in debug log

main.DEBUG: cache_invalidate:  {"method":"GET","url":"http:/","invalidateInfo":{"identifier":"interception"}} []

error in system log

[2020-09-30 09:46:44] main.CRITICAL: Unable to unserialize value. Error: Syntax error [] []

Answer 1

Try to use below class in your construct to serialize and unserialize value.

public function __construct(
    \Magento\Framework\Serialize\Serializer\Json $jsonSerializer
) {
    $this->_jsonSerializer    = $jsonSerializer;
}

Then you can use this functions..

$this->_jsonSerializer->serialize($array);
$this->_jsonSerializer->unserialize($array);

Hope this will help you.