title: PHP - Display a 404 Error without redirecting to another page
body: <p>I want to display a 404 Error if a user reaches a page that exists but I don't want him/her to see.</p>
  
  <p>I don't want to do redirect (that would cause the address bar to show the link of the error page in the address bar) like the following:</p>
  
  <pre><code>if ($this_page_should_not_be_seen)
     header("Location: err.php?e=404");
  </code></pre>
  
  <p>Instead, it should seem like the page really doesn't exist, without having the URL in the browser's address changed.</p>