title: Delete a header in PHP
body: <p>To allow caching a PHP generated file, I want to make sure, that the 'Pragma: no-cache' header is <strong>not</strong> set. However, how do I delete a possibly already set header?</p>
  
  <p>That is, it <em>could</em> be possible, that somewhere in the code someone wrote <code>header('Pragma: no-cache');</code> and now I want to make sure, the header is not sent.</p>
  
  <p>Is it sufficient to do this:</p>
  
  <pre><code>header('Pragma:');
  </code></pre>
  
  <p>or is there something like <code>delete_header()</code> (which would, apparently, be undocumented or well-hidden)?</p>