title: How to make a PHP serial code system
body: <p>I was thinking of implementing a MySQL database with valid serial codes which would be checked against user input and grant usage of the app if the check returns true, but I know this is way too basic since the user (who will be using a localhost based application) could easily crack the database and add his own serials (or at least tell someone else who has got a basic understanding of PHP &amp; SQL if they think apps come out of the "magic box").</p>
  
  <p>Since I have not done this before, is there any popular approach? Or better yet it'd be nice if you just gave me some ideas. </p>