WC_Cart::check_cart_item_validity PHP Method

    public function check_cart_item_validity()
    {
        $return = true;
        foreach ($this->get_cart() as $cart_item_key => $values) {
            $product = $values['data'];
            if (!$product || !$product->exists() || 'trash' === $product->get_status()) {
                $this->set_quantity($cart_item_key, 0);
                $return = new WP_Error('invalid', __('An item which is no longer available was removed from your cart.', 'woocommerce'));
            }
        }
        return $return;
    }