title: How can I eliminate cheating for an online survey?
body: <p>How can I eliminate "as much as possible" cheating on a survey? So I want a survey to be completed by one computer at a time.</p>
  
  <p>I currently capture the IP address but an IP address is a dynamic so that is a problem. Please IP address can be spoofed I think.</p>
  
  <p>So how can I improve my security but allowing only one PC at a time to complete the survey?</p>
  
  <p>"Cheat" means submitting the survey multiple time.
  I created the survey using PHP.</p>
  
  <p>Thanks</p>