title: completely replace an HTML file with another using PHP
body: <p>I am working on a html form, which I only want to be usable once at all.
  So if one person has filled it in, another person should not be able to fill it in again. Not even the same person, and not even if he or she clicks on going back in his or her browser.</p>
  
  <p>So far I have multiple ways in mind what could work:</p>
  
  <ol>
  <li><p>Use PHP to completely replace the form.html page with another .html file, which I have already stored on the server for this purpose, or</p></li>
  <li><p>Use PHP to partly replace the form.html page, even though it has no added value over completely replacing the html page, or</p></li>
  <li><p>Adding a hidden field to my form.html file (which I have to change to a .php page in this case), posting a "1" to a database which I can retrieve everytime the form.php page loads in a way that it shows the form when a 0 is set, and doesn't when a 1 is set. In this case I also wonder if there isn't a simpeler solution to create a database just to store one "1".</p></li>
  </ol>
  
  <p>I know how to use google, and usually I always manage to find a solution, but now I am feeling clueless. Please someone help me with a simple solution. </p>