WooCommerce Custom Checkout Fields

woocommerce-custom-fields.php

<?php

/**
 * Add Fields to Order
 *
 * @param $fields (array) WooCommerce Checkout Fields
 */
add_action( 'woocommerce_checkout_before_customer_details', function( $fields ) {

    // Define new Field
    woocommerce_form_field( 'delivery_date', array(
        'type'          => 'text',
        'class'         => array('nuxley-order-field'),
        'label'         => __('Selected Delivery or Collection Date'),
        'placeholder'   => __('Please select a delivery or collection date.'),
        'required'      => true
    ) );

} );

/**
 * Save Custom Fields
 *
 * Save the input of custom order fields
 *
 * @param $order_id (int) WooCommerce Order ID
 */
add_action( 'woocommerce_checkout_update_order_meta', function( $order_id ) {

    // Check field is not empty
    if ( !empty( $_POST['delivery_date'] ) ) {
        update_post_meta( $order_id, 'Delivery Date', sanitize_text_field( $_POST['delivery_date'] ) );
    }

} );

/**
 * Show custom fields on the Admin Page
 *
 * @param $order (object) WooCommerce Order Object
 */
add_action( 'woocommerce_admin_order_data_after_shipping_address', function( $order ) {

    $value = get_post_meta( $order->get_id(), 'Delivery Date', true );
    printf('<p><strong>%s: </strong><br><input type="text" value="%s"></p>', 'Delivery Date', $value);

}, 10, 1 );