Change Cart total price in WooCommerce - php

Question

I am running into issues with the cart total only displaying 0
Essentially what I am trying to do is only accept a deposit total of a certain amount after all cart items have been added to the carts subtotal.
So for example if the customer adds $100 worth of items, they would only pay $10 initially or (10%) of the subtotal as the total value.
I took the code from here: Change total and tax_total Woocommerce and customize it this way:
add_action('woocommerce_cart_total', 'calculate_totals', 10, 1);
function calculate_totals($wc_price){
$new_total = ($wc_price*0.10);
return wc_price($new_total);
}
But the total amount shows 0.00 when that code is enabled. If removed the code, I get the standard total.
I also could not find on the woocommerce site where the full api is listed, only generic articles related to how to create a plugin.
Any help or a point in the right direction would be great.

Answer 1

This does not answer this question. Loic's does. This is another way of doing it to show a line item of 10% off:
function prefix_add_discount_line( $cart ) {
$discount = $cart->subtotal * 0.1;
$cart->add_fee( __( 'Down Payment', 'yourtext-domain' ) , -$discount );
}
add_action( 'woocommerce_cart_calculate_fees', 'prefix_add_discount_line' );

Answer 2

Since Woocommerce 3.2+
it does not work anymore with the new Class WC_Cart_Totals ...
New answer: Change Cart total using Hooks in Woocommerce 3.2+
First woocommerce_cart_total hook is a filter hook, not an action hook. Also as wc_price argument in woocommerce_cart_total is the formatted price, you will not be able to increase it by 10%. That's why it returns zero.
Before Woocommerce v3.2 it works as some WC_Cart properties can be accessed directly
You should better use a custom function hooked in woocommerce_calculate_totals action hook this way:
// Tested and works for WooCommerce versions 2.6.x, 3.0.x and 3.1.x
add_action( 'woocommerce_calculate_totals', 'action_cart_calculate_totals', 10, 1 );
function action_cart_calculate_totals( $cart_object ) {
if ( is_admin() && ! defined( 'DOING_AJAX' ) )
return;
if ( !WC()->cart->is_empty() ):
## Displayed subtotal (+10%)
// $cart_object->subtotal *= 1.1;
## Displayed TOTAL (+10%)
// $cart_object->total *= 1.1;
## Displayed TOTAL CART CONTENT (+10%)
$cart_object->cart_contents_total *= 1.1;
endif;
}
Code goes in function.php file of your active child theme (or theme) or also in any plugin file.
Is also possible to use WC_cart add_fee() method in this hook, or use it separately like in Cristina answer.