To auto populate the product ID and the product SKU in your booking form (page), you should try this (without any guaranty as it can be tested for real on your page form):
add_action( 'wp_footer', 'autopopulate_product_id_script' );
function autopopulate_product_id_script() {
if( isset( $_GET['id'] ) ):
?>
<script type="text/javascript">
(function($){
$('input[name="productid"]').val("<?php echo $_GET['id']; ?>");
$('input[name="productsku"]').val("<?php echo $_GET['sku']; ?>");
})(jQuery);
</script>
<?php
endif;
}
Code goes in function.php file of your active child theme (or theme) or also in any plugin file.
The product id and the product sku need to be passed in url something like: http//www.example.com/booking-page/?id=124&&sku=AH1584
And your <imput>
text fields should be something like:
<input type="text" name="productid" val="">
<input type="text" name="productsku" val="">
So for the product sku is something similar, that you will be able to add with ease…
But as javascript is already very active in you "Easy Appointments" booking form, I don't know if this will work.
This answer is related to: Add custom "Booking" button to WooCommerce Product single pages