Apply a fee to cart in Woocommerce - php

Question

I am trying to programatically add a fee to the woocommerce cart from a script which is executed on a form submission. As far as I am aware, I don't think I am able to use a hook as I need to apply the custom fee when the form on the page has been submitted (Custom API integration).
I have tried doing the following within the script:
add_action( 'woocommerce_cart_calculate_fees', 'woo_add_cart_fee' );
function woo_add_cart_fee( $cart ){
$valid = false;
if ( ! $_POST || ( is_admin() && ! is_ajax() ) ) {
return;
}
if (isset($_POST['coupon_code'])) {
$code = $_POST['coupon_code'];
$coupon = new WC_Coupon($code);
if($coupon->get_amount() != null){
$valid == true;
}
//if not then lets check to see if its a giftcard.
if($valid == false){
$api_login="xxxxxx";
$api_password="xxxxxx";
$url = "https://xxxxxx.com/xxxxx/xxxxx.svc";
$client = new SoapClient( $url . "?singleWsdl",
array(
"location" => $url,
"login" => $api_login,
"password" => $api_password,
"trace" => 1
)
);
$request = new StdClass();
$request->bonId = $code;
$request->bonType = 'GiftCard';
// call the correct database
$request->context = new StdClass();
$request->context->DatabaseId = 'xxxxx';
try {
$resu = $client->GetBonAvailableAmount($request);
if (isset($resu->GetBonAvailableAmountResult->Amount)) {
$amount = $resu->GetBonAvailableAmountResult->Amount;
$cart->add_fee('xxxxxx Gift Card ', floatval('-'.$amount * 0.83333), false, '' );
} else {
$response['status'] = 'error';
$response['message'] = 'Gift card not recognized.';
}
} catch (Exception $e) {
}
}
}
}
and I can see that when I echo the cart object there is a fee object which contains all the correct data.
It seems that the cart or totals are not updating, if i refresh the page, they still do not reflect the values i am expected.
I have trawled pretty much all Stack Overflow posts and cant seem to find anything which solves the issue.
Is there anything that I am missing here?

Answer 1

You need to use a custom function hooked in woocommerce_cart_calculate_fees action hook:
add_action( 'woocommerce_cart_calculate_fees', 'add_a_custom_fee', 10, 1 );
function add_a_custom_fee( $cart ) {
$amount = 20;
$cart->add_fee( __('Custom fee'), $amount );
}
Code goes in function.php file of your active child theme (or active theme). Tested and works.