Check that a variable is an instance of a Class Object in WooCommerce

Question

I am running a function whereby I check if a user has a refunded item/s on their previous order and if they do then apply a credit as a negative cart fee at checkout. The function is working for users who have placed an order before but is causing a critical error on the site for new users.

Fatal error: Uncaught Error: Call to a member function get_refunds() on bool in /wp-content/themes/my-theme/refunds.php:20 Stack trace:  
#0 /wp-includes/class-wp-hook.php(287): add_last_order_refund_total_at_checkout(Object(WC_Cart))  
#1 /wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters('', Array)  
#2 /wp-includes/plugin.php(478): WP_Hook->do_action(Array)  
#3 /wp-content/plugins/woocommerce/includes/class-wc-cart.php(1714): do_action('woocommerce_car...', Object(WC_Cart))  
#4 /wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php(270): WC_Cart->calculate_fees()  
#5 /wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php(829): WC_Cart_Totals->get_fees_from_cart()  
#6 /wp-content/plugins/woocommerce/includes/class-wc- in /wp-content/themes/my-theme/refunds.php on line 20

Here is the code to check for any refunds on the previous order:

//Check total of refunded items from last order - add as a fee at checkout
function add_last_order_refund_total_at_checkout($cart_object){
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    $user_id = get_current_user_id(); // The current user ID
    $customer = new WC_Customer( $user_id );
    $last_order = $customer->get_last_order();
    $order_id = $last_order;

    // Get the WC_Order Object instance (from the order ID)
    $order = wc_get_order( $order_id );

    // Get the Order refunds (array of refunds)
    $order_refunds = $order->get_refunds();
    $total_to_refund = $order->get_total_refunded()*(-1);//WIP need to check which items have tax
    
    if (!empty($order_refunds)) WC()->cart->add_fee( 'Refund', $total_to_refund  );  
}
add_action( 'woocommerce_cart_calculate_fees', 'add_last_order_refund_total_at_checkout', 10, 1 );

I believe I need to first check to see if a user has any previous orders otherwise the get_refund() is causing an error as their aren't any orders to check? How would I safely do this?

LoicTheAztec · Accepted Answer · 2020-08-04 00:43:14Z

If you look to WC_Customer get_last_order() method documentation or source code, you will see:

/*
 * @return WC_Order|false
 */

which means that get_last_order() method can return alternatively:

the WC_Order object
or false boolean value.

So you can just use in your code:

$last_order = $customer->get_last_order();

if ( ! $last_order )  {
   return; // Exit (Not an order)
}

To avoid this error.

Now you can use is_a() php conditional functions to check that a variable is a from a specific Object class and not something else like:

$last_order = $customer->get_last_order();

if ( ! is_a( $last_order, 'WC_Order' ) ) {
   return; // Exit (Not an order)
}

// Your other code…

Or you can use method_exists() php conditional functions for WC_Order get_refunds() method, to check that the a variable is a from a specific Object class and not something else:

$last_order = $customer->get_last_order();

if ( ! method_exists( $last_order, 'get_refunds' ) )  {
   return; // Exit (Not an order)
}

// Your other code…

The three cases work nicely, avoiding an error

7uc1f3r · Accepted Answer · 2020-08-02 20:53:57Z

Give it a try this way, multiple controls have been added, see comments

// Check total of refunded items from last order - add as a fee at checkout
function add_last_order_refund_total_at_checkout( $cart ) {
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    // The current user ID
    $user_id = get_current_user_id();
    
    // User id exists
    if ( $user_id > 0 ) {
        $customer = new WC_Customer( $user_id );
        
        // Get last order
        $last_order = $customer->get_last_order();

        // True
        if ( $last_order ) {

            // Get the order id
            $order_id = $last_order->get_id();
        
            // Order ID exists
            if ( is_numeric( $order_id ) ) {
                // Get the WC_Order Object instance (from the order ID)
                $order = wc_get_order( $order_id );

                // Get the Order refunds (array of refunds)
                $order_refunds = $order->get_refunds();
            
                // NOT empty
                if ( ! empty( $order_refunds) ) {
                    // WIP need to check which items have tax
                    $total_to_refund = $order->get_total_refunded();
                
                    // Add fee
                    $cart->add_fee( 'Refund', $total_to_refund  );
                }
            }
        }
    }
}
add_action( 'woocommerce_cart_calculate_fees', 'add_last_order_refund_total_at_checkout', 10, 1 );

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