Woocommerce created fee is not saved in order

add a custom checkbox field to the WooCommerce checkout page after the order notes section. It uses the woocommerce_after_order_notes action hook to add the field. The add_custom_checkbox_to_checkout function is responsible for rendering the checkbox field. It uses the woocommerce_form_field function to generate the checkbox field HTML. The value of the checkbox is retrieved from the WooCommerce session using WC()->session->get('handwritten_card').

// Add the custom checkbox field to the checkout page
add_action( 'woocommerce_after_order_notes', 'add_custom_checkbox_to_checkout' );
function add_custom_checkbox_to_checkout( $checkout ) {
    echo '<div id="custom_checkbox_field">';
    // Generate the checkbox field with the label "Handwritten Card"
    woocommerce_form_field( 'handwritten_card', array(
        'type' => 'checkbox',
        'class' => array( 'input-checkbox' ),
        'label' => 'Handwritten Card',
    ), WC()->session->get( 'handwritten_card' ));
    echo '</div>';
}

add a JavaScript script to the footer of the page using the wp_footer action hook. The script uses jQuery to detect the change event of the checkbox and triggers the update_checkout event when the checkbox is changed. This event is used to update the checkout page and recalculate the totals.

// Add JavaScript script to handle checkbox change event
add_action( 'wp_footer', 'custom_checkbox_script' );
function custom_checkbox_script() {
    ?>
    <script type="text/javascript">
        jQuery(document).ready(function($) {
            // Detect checkbox change event
            $(document).on('change', '#handwritten_card', function() {
                $(document.body).trigger('update_checkout');
            });
        });
    </script>
    <?php
}

Below code defines the woo_add_cart_fee function, which is hooked to the woocommerce_cart_calculate_fees action. This function is responsible for adding a fee to the cart when the checkbox is checked and removing the fee when the checkbox is unchecked. It first checks if the request is a valid submission and then parses the POST data to retrieve the checkbox value. The checkbox value in the session is reset to null. If the checkbox is checked, it adds a fee named "Gift card" with a value of 2 to the cart using $woocommerce->cart->add_fee(). It also sets the checkbox value in the WooCommerce session using WC()->session->set('handwritten_card', sanitize_text_field($data['handwritten_card'])). If the checkbox is unchecked, it removes the "Gift card" fee from the cart using $woocommerce->cart->remove_fee().

// Add or remove a fee based on the checkbox value
function woo_add_cart_fee() {
    global $woocommerce;

    // Check if the request is a valid submission
    if ( ! $_POST || ( is_admin() && ! is_ajax() ) ) {
        return;
    }

    // Parse the POST data to retrieve the checkbox value
    parse_str($_POST['post_data'], $data);

    // Reset the checkbox value in the session
    WC()->session->set( 'handwritten_card', null );

    // Check if the checkbox is checked
    if ( isset( $data['handwritten_card'] ) && $data['handwritten_card'] == 1 ) {
        // Add a fee to the cart named "Gift card" with a value of 2
        $woocommerce->cart->add_fee( 'Gift card', 2, true, '' );
        // Set the checkbox value in the session
        WC()->session->set( 'handwritten_card', sanitize_text_field( $data['handwritten_card'] ) );
    } else {
        // Remove the "Gift card" fee from the cart if the checkbox is unchecked
        foreach ( $woocommerce->cart->get_fees() as $fee_key => $fee ) {
            if ( $fee->name === 'Gift card' ) {
                $woocommerce->cart->remove_fee( $fee_key );
                break;
            }
        }
    }
}
add_action( 'woocommerce_cart_calculate_fees', 'woo_add_cart_fee' );

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