Add custom radio buttons to Woo checkout

add-custom-radio-buttons-to-woo-checkout.php

<?php 
/* 
    Add custom delivery radio buttons to checkout.
    Requires WooCommerce v3+
    
    Add your radio buttons.
    Remove the 'required' attribute if these are to be optional.
*/
add_action( 'woocommerce_review_order_before_payment', 'display_extra_fields_after_billing_address' , 10, 1 );
function display_extra_fields_after_billing_address () { ?>
    <h3>Delivery Options <sup>*</sup></h3>
    <p><input type="radio" name="delivery_option" value="Collect from the depot." required /> Collect from the depot.</p>
    <p><input type="radio" name="delivery_option" value="Leave the consignment without a signature." /> Leave the consignment without a signature.</p>
  <?php 
}

add_action( 'woocommerce_checkout_update_order_meta', 'add_delivery_option_to_order' , 10, 1);
function add_delivery_option_to_order ( $order_id ) {
    if ( isset( $_POST ['delivery_option'] ) &&  '' != $_POST ['delivery_option'] ) {
        add_post_meta( $order_id, '_delivery_option',  sanitize_text_field( $_POST ['delivery_option'] ) );
    }
}

/*
    Include selected option in notification emails.
*/
add_filter( 'woocommerce_email_order_meta_fields', 'add_delivery_option_to_emails' , 10, 3 );
function add_delivery_option_to_emails ( $fields, $sent_to_admin, $order ) {
	
    if( version_compare( get_option( 'woocommerce_version' ), '3.0.0', '>=' ) ) {            
	$order_id = $order->get_id();
    } else {
	$order_id = $order->id;
    }

    $delivery_option = get_post_meta( $order_id, '_delivery_option', true );

    if ( '' != $delivery_option ) {
	$fields[ 'Delivery Date' ] = array(
	    'label' => __( 'Delivery Option', 'delivery_option' ),
	    'value' => $delivery_option,
	);
    }
    return $fields;
}

/*
    Validation nag.
    Remove this if the fields are to be optional.
*/
function action_woocommerce_after_checkout_validation( $data, $errors ) { 
    if ( empty( $_POST['delivery_option'] ) ) :
        $errors->add( 'required-field', __( 'You have not chosen a delivery option.', 'woocommerce' ) );
    endif;
}
add_action( 'woocommerce_after_checkout_validation', 'action_woocommerce_after_checkout_validation', 10, 2 );


/*
    Display field value on the order edit page.
*/
add_action( 'woocommerce_admin_order_data_after_billing_address', 'my_custom_checkout_field_display_admin_order_meta', 10, 1 );
function my_custom_checkout_field_display_admin_order_meta($order) {
    echo '<p><strong>'.__('Delivery Option').':</strong> <br/>' . get_post_meta( $order->get_id(), '_delivery_option', true ) . '</p>';
}

@brock39 Your link is a 404