Ttdfjt

Getting below issue at checkout step after upgrade of magento to 2.3.1 from 2.1.8.

1 exception(s):
Exception #0 (InvalidArgumentException): Unable to serialize value.

Exception #0 (InvalidArgumentException): Unable to serialize value.
<pre>#1 MagentoCheckoutBlockOnepage->getSerializedCheckoutConfig() called at [vendor/magento/module-checkout/view/frontend/templates/onepage.phtml:26]
#2 include('/var/www/project...') called at [vendor/magento/framework/View/TemplateEngine/Php.php:59]
#3 MagentoFrameworkViewTemplateEnginePhp->render(&MagentoCheckoutBlockOnepageInterceptor#000000001d8c0f290000000035fe6de3#, '/var/www/project...', array()) called at [vendor/magento/framework/View/Element/Template.php:271]
#4 MagentoFrameworkViewElementTemplate->fetchView('/var/www/project...') called at [vendor/magento/framework/View/Element/Template.php:301]
#5 MagentoFrameworkViewElementTemplate->_toHtml() called at [vendor/magento/framework/View/Element/AbstractBlock.php:668]
#6 MagentoFrameworkViewElementAbstractBlock->toHtml() called at [vendor/magento/framework/View/Layout.php:557]
#7 MagentoFrameworkViewLayout->_renderBlock('checkout.root') called at [vendor/magento/framework/View/Layout.php:533]
#8 MagentoFrameworkViewLayout->renderNonCachedElement('checkout.root') called at [vendor/magento/framework/View/Layout.php:488]
#9 MagentoFrameworkViewLayout->renderElement('checkout.root', false) called at [vendor/magento/framework/View/Layout.php:585]
#10 MagentoFrameworkViewLayout->_renderContainer('content', false) called at [vendor/magento/framework/View/Layout.php:535]
#11 MagentoFrameworkViewLayout->renderNonCachedElement('content') called at [vendor/magento/framework/View/Layout.php:488]
#12 MagentoFrameworkViewLayout->renderElement('content', false) called at [vendor/magento/framework/View/Layout.php:585]
#13 MagentoFrameworkViewLayout->_renderContainer('main', false) called at [vendor/magento/framework/View/Layout.php:535]
#14 MagentoFrameworkViewLayout->renderNonCachedElement('main') called at [vendor/magento/framework/View/Layout.php:488]

Please let me know if someone faced this before.

Magento replaced the serialization by Json in 2.2.2 and later. So it may requires to updates all the database values that were previously saved by serialization.

To patch it and get everything working you try the following patch:

File: /vendor/magento/framework/Serialize/Serializer/Json.php

Find:

public function unserialize($string)

 $result = json_decode($string, true);
 if (json_last_error() !== JSON_ERROR_NONE) 
 throw new InvalidArgumentException('Unable to unserialize value.');
 
 return $result;

replace by:

public function unserialize($string)

 $result = json_decode($string, true);
 if (json_last_error() !== JSON_ERROR_NONE) 
 if(false !== @unserialize($string))
 return unserialize($string);
 
 throw new InvalidArgumentException('Unable to unserialize value.');
 
 return $result;