Looking to generate an invoice using product tables

I can see two approaches to this, either you make an e-shop like application that your users browse all products in stock and add them to a cart. And then "check out" the cart to a customer.

Or you will utilize a search function on your invoice page so users can search for the item (search automatically with ajax), but that would mean they know what they are looking for. And would be harder to find something you don't know the name of (as you can't browse the inventory).

The functionally you are searching for are JavaScript and AJAX depending, and you need to read up on that instead. :-)
Ajax for sending inputs (searching) and return available products. And how many are in stock.

After an item and quantity a user press "add" and it gets copied to an table with all items (with JavaScript).

https://code.tutsplus.com/tutorials/how-...-cms-32494

Thanks, this is good advice and along the lines of what I was thinking. I have done this on other projects using Procedural PHP.  I was told that a framework would make this easier to accomplish, but I am not sure I can afford the time for the learning curve at this point if I will be using ajax and jquery primarily.  I appreciate your input, many thanks.