woocommerce 结帐页面添加自定义费用字段ajax更新

add_action( 'woocommerce_after_checkout_billing_form', 'add_box_option_to_checkout' );

function add_box_option_to_checkout( $checkout ) {

    echo '<div id="message_fields">';

    woocommerce_form_field( 'add_gift_box', array(

        'type'          => 'checkbox',

        'class'         => array('add_gift_box form-row-wide'),

        'label'         => __('Ilość pudełek ozdobnych - 25 PLN/szt'),

        'placeholder'   => __(''),

        ), $checkout->get_value( 'add_gift_box' ));

        echo '</div>';

}

add_action( 'wp_footer', 'woocommerce_add_gift_box' );

function woocommerce_add_gift_box() {

    if (is_checkout()) {

    ?>

    <script type="text/javascript">

    jQuery( document ).ready(function( $) {

        $('#add_gift_box').click(function(){

            jQuery('body').trigger('update_checkout');

        });

    });

    </script>

    <?php

    }

}

add_action( 'woocommerce_cart_calculate_fees', 'woo_add_cart_fee' );

function woo_add_cart_fee( $cart ){

        if ( ! $_POST || ( is_admin() && ! is_ajax() ) ) {

        return;

    }

    if ( isset( $_POST['post_data'] ) ) {

        parse_str( $_POST['post_data'], $post_data );

    } else {

        $post_data = $_POST; // fallback for final checkout (non-ajax)

    }

    if (isset($post_data['add_gift_box'])) {

        $extracost = 25; // not sure why you used intval($_POST['state']) ?

        WC()->cart->add_fee( 'Ozdobne pudełka:', $extracost );

    }

}