WordPress – Argument #1 ($array) must be of type array, null given in wc-cart-functions.php

I recently came across this intriguing error. I searched online and did not find anything that helped much, so I decided to write this post with a solution.

Here is the full error: PHP Fatal error: Uncaught TypeError: array_keys(): Argument #1 ($array) must be of type array, null given in /yourwpfolder/wp-content/plugins/woocommerce/includes/wc-cart-functions.php:476. The line may vary depending on your WooCommerce version.

Let's go to the solution. Initially, the quickest fix is to create a new shipping zone for locations not covered by your other shipping zones. In my case, I did it as shown below, and it solved the issue:

The menu is located at WooCommerce > Settings > Shipping.

Another solution mentioned online is disabling all plugins except WooCommerce and repeating the checkout process. Some plugins can affect shipping methods and cause this error.