I am using the code snippet below to limit the purchase of one unique WooCommerce product per order, because of logistic reasons (multiple warehouses). I use an attribute to specify the warehouse and it would be convenient to allow customers to order multiple products if the warehouse/attribute is the same. Could someone help me with changing the code snippet? add_filter( 'woocommerce_add_to_cart_validation', 'wc_limit_one_per_order', 10, 2 ); function wc_limit_one_per_order( $passed_validation, $product_id ) { if ( WC()->cart->get_cart_contents_count() >= 1 ) { wc_add_notice( __( 'This product cannot be purchased with other products. Please, empty your cart first and then add it again.', 'woocommerce' ), 'error' ); return false; } return $passed_validation; } I thought adding something like this, but I don't know how to proceed.. $attribute = $product->get_attribute('pa_warehouse'); foreach (WC()->cart->get_cart() as $cart_item_key => $values) { $product = $values['data'];