Imagine that you're selling a digital product online. Maybe you've written an article or a book and want to sell it on your site as a PDF. There are many ways one could do this, but one of the more convenient is to provide the user with a unique URL that only will work a limited number of times.
This URL could, for example, be presented to the user (your client) on the last page of an orderflow, after payment has been made. We will look at code to generate a unique URL that will work a single time.