php - Display custom meta data in WooCommerce admin order after billing address

one text

Solution:

The problem comes from $order->id, so try the following instead:

add_action('woocommerce_admin_order_data_after_billing_address', 'wps_select_checkout_field_display_admin_order_meta', 10, 1 );
function wps_select_checkout_field_display_admin_order_meta( $order ) {
    $delivery_time = $order->get_meta('delivery_time');
    
    if ( ! empty($delivery_time) ) {
        echo '<p><strong>'.__('Requested Delivery Time').':</strong> ' . $delivery_time . '</p>';
    }
}

Now it should work.