title: ETag header not being sent from PHP
body: <p>I'm running PHP 5.3.2 and Apache 2.2.14. Using <code>header()</code>, If I send "ETagx" I get the header in the response, but if I send "ETag", the correct header name, I get nothing.</p>
  
  <p><code>header('ETagx: "33653a-4831d8249af80"')</code></p>
  
  <p>works, while</p>
  
  <p><code>header('ETag: "33653a-4831d8249af80"')</code></p>
  
  <p>does not. Is there a configuration option in php.ini, or in any of the Apache configuration files that might affect this?</p>