turnaround.php

<?php
/**
 * Snippet: Add a 'Shipping speed' radio field (Standard / Express) to the checkout page,
 * inside the order review table immediately below the subtotal row and above the
 * shipping/payment method options.
 *
 * Selecting 'Express' adds a 15% fee based on the cart's current total.
 * The field is saved to the order as post meta and shown on the admin order screen.
 *
 * Usage: add this file as an mu-plugin, or require it from your theme/child-theme
 * functions.php, or paste the contents into a plugin such as Code Snippets.
 */

define( 'CSSR_FIELD_KEY', 'shipping_speed' );
define( 'CSSR_EXPRESS_FEE_PERCENT', 15 );

/**
 * Render the radio field as a row in the order review table, right after the
 * cart subtotal row and before shipping/payment methods are shown.
 */
add_action( 'woocommerce_review_order_after_cart_contents', 'cssr_render_shipping_speed_field' );
function cssr_render_shipping_speed_field() {

	$chosen = WC()->session ? WC()->session->get( CSSR_FIELD_KEY, 'standard' ) : 'standard';

	?>
	<tr class="cssr-shipping-speed">
		<th><?php esc_html_e( 'Shipping speed', 'woocommerce' ); ?></th>
		<td>
			<div id="cssr_shipping_speed_field">
				<?php
				woocommerce_form_field(
					CSSR_FIELD_KEY,
					array(
						'type'    => 'radio',
						'class'   => array( 'cssr-shipping-speed-field form-row-wide' ),
						'options' => array(
							'standard' => __( 'Standard', 'woocommerce' ),
							'express'  => sprintf(
								/* translators: %d: express fee percentage */
								__( 'Express (+%d%% of cart total)', 'woocommerce' ),
								CSSR_EXPRESS_FEE_PERCENT
							),
						),
						'required' => true,
					),
					$chosen
				);
				?>
			</div>
		</td>
	</tr>
	<?php
}

/**
 * Require a selection before allowing the order to be placed.
 */
add_action( 'woocommerce_checkout_process', 'cssr_validate_shipping_speed_field' );
function cssr_validate_shipping_speed_field() {
	if ( empty( $_POST[ CSSR_FIELD_KEY ] ) ) {
		wc_add_notice( __( 'Please choose a shipping speed.', 'woocommerce' ), 'error' );
	}
}

/**
 * Persist the selection to the order and session so it survives page reloads
 * and is available when the fee is calculated.
 */
add_action( 'woocommerce_checkout_create_order', 'cssr_save_shipping_speed_to_order', 10, 2 );
function cssr_save_shipping_speed_to_order( $order, $data ) {
	if ( ! empty( $_POST[ CSSR_FIELD_KEY ] ) ) {
		$value = sanitize_text_field( wp_unslash( $_POST[ CSSR_FIELD_KEY ] ) );
		$order->update_meta_data( '_' . CSSR_FIELD_KEY, $value );
	}
}

/**
 * Keep the chosen value in the WC session, updated on every checkout field change,
 * so the cart fee recalculates live via AJAX (woocommerce_update_order_review).
 */
add_action( 'woocommerce_checkout_update_order_review', 'cssr_store_shipping_speed_in_session' );
function cssr_store_shipping_speed_in_session( $post_data ) {
	parse_str( $post_data, $data );

	$value = isset( $data[ CSSR_FIELD_KEY ] ) ? sanitize_text_field( wp_unslash( $data[ CSSR_FIELD_KEY ] ) ) : 'standard';

	WC()->session->set( CSSR_FIELD_KEY, $value );
}

/**
 * Add the 15% express fee to the cart when 'Express' is selected.
 */
add_action( 'woocommerce_cart_calculate_fees', 'cssr_add_express_fee' );
function cssr_add_express_fee( $cart ) {

	if ( is_admin() && ! defined( 'DOING_AJAX' ) ) {
		return;
	}

	if ( ! WC()->session ) {
		return;
	}

	$shipping_speed = WC()->session->get( CSSR_FIELD_KEY );

	if ( 'express' !== $shipping_speed ) {
		return;
	}

	$fee = $cart->get_cart_contents_total() * ( CSSR_EXPRESS_FEE_PERCENT / 100 );

	if ( $fee > 0 ) {
		$cart->add_fee( __( 'Express shipping fee (15%)', 'woocommerce' ), $fee, true );
	}
}

/**
 * Show the chosen shipping speed on the admin order edit screen.
 */
add_action( 'woocommerce_admin_order_data_after_billing_address', 'cssr_display_shipping_speed_in_admin' );
function cssr_display_shipping_speed_in_admin( $order ) {
	$value = $order->get_meta( '_' . CSSR_FIELD_KEY );

	if ( ! $value ) {
		return;
	}

	$label = 'express' === $value ? __( 'Express', 'woocommerce' ) : __( 'Standard', 'woocommerce' );

	echo '<p><strong>' . esc_html__( 'Shipping speed', 'woocommerce' ) . ':</strong> ' . esc_html( $label ) . '</p>';
}