title: How to handle multiple submissions server-side
body: <p>We all know the good old "disable the submit button" trick but what are the best ways to handle multiple submissions server side? I have an application where it is absolutely <em>critical</em> that a form only be sent once - it processes a credit card. I didn't write how it is right now but as a quick fix I threw on the disable-on-submit technique, however some impatient users that have javascript disabled are still getting charged twice.</p>
  
  <p>So, what are ways to avoid this? I can think of a few - I have used a few in the past - but I'd like to see if there's any "best practices" on how to tackle this one. I am using PHP but I'm more interested in concepts.</p>
  
  <p><strong>edit:</strong> I am aware of the token technique and it is what I have used in the past, this question is more or less to see if my approach is in line with what the rest of you fine programmers use.</p>