Pre-fill WooCommerce billing fields with string url - php

Question

I have a Wordpress site with WooCommerce webshop and a client (hotel) that wants customers to order products in my webshop. I want those customers not to have to fill in the hotel information during checkout (the products are delivered to their room).
I have build a custom page for the hotel where people can place certain products in the cart, and when they want to checkout they press a custom checkout button that prefills the checkout fields. I am using this technique to achieve this: https://newpulselabs.com/prefill-checkout-fields-cartflows/
// Autofill checkout fields from URL
add_filter( 'woocommerce_checkout_fields' , 'prefill_billing_fields' );
function prefill_billing_fields ( $address_fields ) {
// Get the data from the URL
if ( isset( $_GET['fname'] ) || isset( $_GET['lname'] ) || isset( $_GET['email'] ) || isset( $_GET['company'] ) )
{
// wp_die();
$fname = isset( $_GET['fname'] ) ? esc_attr( $_GET['fname'] ) : '';
$lname = isset( $_GET['lname'] ) ? esc_attr( $_GET['lname'] ) : '';
$em = isset( $_GET['email'] ) ? esc_attr( $_GET['email'] ) : '';
$company = isset( $_GET['company'] ) ? esc_attr( $_GET['company'] ) : '';
// First Name
if( isset($_GET['fname']) && ! empty($_GET['fname']) ){
if( isset( $address_fields['billing']['billing_first_name'] ) ){
$address_fields['billing']['billing_first_name']['default'] = $fname;
}
}
// Last Name
if( isset($_GET['lname']) && ! empty($_GET['lname']) ){
if( isset( $address_fields['billing']['billing_last_name'] ) ){
$address_fields['billing']['billing_last_name']['default'] = $lname;
}
}
// Email
if( isset($_GET['email']) && ! empty($_GET['email']) ){
if(isset( $address_fields['billing']['billing_email'] )){
$address_fields['billing']['billing_email']['default'] = $em;
}
}
// Company
if( isset($_GET['company']) && ! empty($_GET['company']) ){
if(isset( $address_fields['billing']['billing_company'] )){
$address_fields['billing']['billing_company']['default'] = $company;
}
}
}
return $address_fields;
}
The url looks like this:
https://www.yourweburl.com/checkout-page/?email=name#example.com&fname=John&lname=Smith&company=ABC Company
And it works perfectly… for new visitors. If a visitor happened to have ordered before in the webshop (and used a different billing address) then that is stored locally in the browser and auto filled.
This technique will not overwrite existing/previous autofill values. I think because it is checking if the cell is empty or not:
if( isset($_GET['fname']) && ! empty($_GET['fname']) ){
if( isset( $address_fields['billing']['billing_first_name'] ) ){
$address_fields['billing']['billing_first_name']['default'] = $fname;
}
}
I tried disabling autofill on the checkout page with this:
add_filter('woocommerce_checkout_get_value','__return_empty_string', 1, 1);
Again that works so well that it removes all prefilled text. So it also removes the information I want to prefill. It works too good ;)
I prefer to alter the first code so that it always overwrites existing values, regardless of what is stored in the browser.
Can anyone help point me in the right direction of how to change the code?
Thanks a lot!
Koen