Update fee dynamically based on radio buttons in Woocommerce checkout

Code updated on 2019: Works for non logged users too and on last WooCommerce version 3.7.x

This needs Ajax and can not be done without it… Here is the Ajax way. In this code you got everything, so remove your related customizations before trying it (meaning remove your radio buttons from template and all related code)…

The complete code (nothing else needed):

// Customizing Woocommerce radio form field
add_action( 'woocommerce_form_field_radio', 'custom_form_field_radio', 20, 4 );
function custom_form_field_radio( $field, $key, $args, $value ) {
    if ( ! empty( $args['options'] ) && is_checkout() ) {
        $field = str_replace( '</label><input ', '</label><br><input ', $field );
        $field = str_replace( '<label ', '<label style="display:inline;margin-left:8px;" ', $field );
    }
    return $field;
}

// Add a custom dynamic packaging fee
add_action( 'woocommerce_cart_calculate_fees', 'add_packaging_fee', 20, 1 );
function add_packaging_fee( $cart ) {
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    $packing_fee = WC()->session->get( 'chosen_packing' ); // Dynamic packing fee
    $fee = $packing_fee === 'box' ? 9.00 : 3.00;
    $cart->add_fee( __( 'Packaging fee', 'woocommerce' ), $fee );
}

// Add a custom radio fields for packaging selection
add_action( 'woocommerce_review_order_after_shipping', 'checkout_shipping_form_packing_addition', 20 );
function checkout_shipping_form_packing_addition() {
    $domain = 'woocommerce';

    echo '<tr class="packing-select"><th>' . __('Packing options', $domain) . '</th><td>';

    $chosen   = WC()->session->get('chosen_packing');
    $chosen   = empty($chosen) ? WC()->checkout->get_value('radio_packing') : $chosen;
    $chosen   = empty($chosen) ? 'bag' : $chosen;

    // Add a custom checkbox field
    woocommerce_form_field( 'radio_packing', array(
        'type' => 'radio',
        'class' => array( 'form-row-wide packing' ),
        'options' => array(
            'bag' => __('In a bag '.wc_price(3.00), $domain),
            'box' => __('In a gift box '.wc_price(9.00), $domain),
        ),
        'default' => $chosen,
    ), $chosen );

    echo '</td></tr>';
}

// jQuery - Ajax script
add_action( 'wp_footer', 'checkout_shipping_packing_script' );
function checkout_shipping_packing_script() {
    if ( ! is_checkout() )
        return; // Only checkout page
    ?>
    <script type="text/javascript">
    jQuery( function($){
        $('form.checkout').on('change', 'input[name=radio_packing]', function(e){
            e.preventDefault();
            var p = $(this).val();
            $.ajax({
                type: 'POST',
                url: wc_checkout_params.ajax_url,
                data: {
                    'action': 'woo_get_ajax_data',
                    'packing': p,
                },
                success: function (result) {
                    $('body').trigger('update_checkout');
                    console.log('response: '+result); // just for testing | TO BE REMOVED
                },
                error: function(error){
                    console.log(error); // just for testing | TO BE REMOVED
                }
            });
        });
    });
    </script>
    <?php

}

// Php Ajax (Receiving request and saving to WC session)
add_action( 'wp_ajax_woo_get_ajax_data', 'woo_get_ajax_data' );
add_action( 'wp_ajax_nopriv_woo_get_ajax_data', 'woo_get_ajax_data' );
function woo_get_ajax_data() {
    if ( isset($_POST['packing']) ){
        $packing = sanitize_key( $_POST['packing'] );
        WC()->session->set('chosen_packing', $packing );
        echo json_encode( $packing );
    }
    die(); // Alway at the end (to avoid server error 500)
}

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

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