Re-calculate totals after setting cart item prices in Woocommerce

Question

How i can change subtotal price after i changed the price of product by the set_price() method? Now it is calculate the total cost at old prices in review-order.php.

cart.php

foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
  ...
  $_product = apply_filters( 'woocommerce_cart_item_product', $cart_item['data'], $cart_item, $cart_item_key );
  $product_id = apply_filters( 'woocommerce_cart_item_product_id', $cart_item['product_id'], $cart_item, $cart_item_key );
  ...
  $_product->set_price( $price );
  ...
}

Answer 1

Ran into this issue where the cart_item's line_total and the cart totals were not updating after programmatically updating existing items in the cart. The woocommerce_before_calculate_totals was not running so that does not fully solve the question in these cases.

In my case, because this was updated on the server side and not through a WooCommerce form my assumption is woocommerce_before_calculate_totals hook was not ran automatically.

Easy enough, you can explicitly tell WooCommerce to recalculate with:

WC()->cart->calculate_totals();

So if you have a woocommerce_before_calculate_totals hook it should be called after this, or WooCommerce should handle it as is just fine.

Answer 2

This need to be done in a specific dedicated hooked function instead of cart.php template:

add_action( 'woocommerce_before_calculate_totals', 'changing_cart_item_prices', 20, 1 );
function changing_cart_item_prices( $cart ) {
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    if ( did_action( 'woocommerce_before_calculate_totals' ) >= 2 )
        return;

    // Loop through cart items
    foreach ( $cart->get_cart() as $cart_item_key => $cart_item ) {
        // The instance of the WC_Product Object
        $product = $cart_item['data'];
        $product_id = $product->get_id(); // The product ID

        $price = $product->get_price(); // The product price

        $new_price = 50;

        // Set the new cart item price
        $product->set_price( $new_price );
    }
}

Code goes in function.php file of your active child theme (or active theme). Tested and work.

Everything will be updated correctly as the hook is ajax powered