Warning: Illegal offset type in vendor/magento/module-catalog/Model/CategoryRepository.php on line 133

Question

I am getting

Warning: Illegal offset type in vendor/magento/module-catalog/Model/CategoryRepository.php on line 133

on product details page in Magento 2.1.8 Which is caused by

vendor/magento/module-catalog/Block/Product/ListProduct.php(114)

Please refer screenshot - code from ListProduct.php

Code from CategoryRepository.php

Answer 1

Had the same issue in 2.1.8. Though for me it only occured when the FPC was enabled. It seems to be caused by:

$this->setCategoryId(current($categories->getIterator()));

in vendor/magento/module-catalog/Block/Product/ListProduct.php. An issue that was fixed in Magento 2.2.0. New code is:

$this->setCategoryId(current($categories->getIterator())->getId());

Upgrading to 2.2.x should resolve the issue. If that's not an option you could also try disabling FPC.