title: Is Content-Transfer-Encoding an HTTP header?
body: <p>I'm writing a web service that returns a base64-encoded PDF file, so my plan is to add two headers to the response:</p>
  
  <pre><code>Content-Type: application/pdf
  Content-Transfer-Encoding: base64
  </code></pre>
  
  <p>My question is: Is <code>Content-Transfer-Encoding</code> a valid HTTP header?  I think it might only be for MIME.  If not, how should I craft my HTTP response to represent the fact that I'm returning a base64-encoded PDF?  Thanks.</p>
  
  <p><strong>EDIT:</strong> </p>
  
  <p>It looks like HTTP does not support this header.  From <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html">RFC2616 Section 14</a>:</p>
  
  <blockquote>
    <p>Note: while the definition of Content-MD5 is exactly the same for HTTP
    as in RFC 1864 for MIME entity-bodies, there are several ways in which
    the application of Content-MD5 to HTTP entity-bodies differs from its
    application to MIME entity-bodies. One is that <strong>HTTP, unlike MIME, does
    not use Content-Transfer-Encoding</strong>, and does use Transfer-Encoding and
    Content-Encoding.</p>
  </blockquote>
  
  <p>Any ideas for what I should set my headers to?  Thanks.</p>
  
  <p><strong>EDIT 2</strong></p>
  
  <p>Many of the code samples found in the comments of this PHP reference manual page seem to suggest that it actually <em>is</em> a valid HTTP header:</p>
  
  <p><a href="http://php.net/manual/en/function.header.php">http://php.net/manual/en/function.header.php</a></p>