Add Placeholders for Checkout Billing Fields Page

add_filter('woocommerce_checkout_fields', 'custom_override_checkout_fields');

  function custom_override_checkout_fields($fields) {

  //Remove billing fields
  unset($fields['billing']['billing_company']);
  unset($fields['order']['order_comments']);

  //Adding Placeholder
  $fields['billing']['billing_first_name']['placeholder'] = 'First Name';
  $fields['billing']['billing_last_name']['placeholder'] = 'Last Name';
  $fields['billing']['billing_email']['placeholder'] = 'Email';
  $fields['billing']['billing_phone']['placeholder'] = 'Phone';
  $fields['billing']['billing_address_1']['placeholder'] = 'Street address';
  $fields['billing']['billing_city']['placeholder'] = 'Town / City';
  $fields['billing']['billing_state']['placeholder'] = 'State';
  $fields['billing']['billing_postcode']['placeholder'] = 'Postcode / Zip';

  return $fields;
  }
  
  add_filter("woocommerce_checkout_fields", "order_fields");

  //Remove Order Notes Field
  add_filter('woocommerce_enable_order_notes_field', '__return_false');