title: What could be adding "Pragma:no-cache" to my response Headers? (Apache, PHP)
body: <p>I have a website which maintenance I've inherited, which is a big hairy mess.<br>
  One of the things I'm doing is improving performance. Among other things, I'm adding <code>Expires</code> headers to images.</p>
  
  <p>Now, there are some images that are served through a PHP file, and I notice that they do have the <code>Expires</code> header, but they also get loaded every time.</p>
  
  <p>Looking at Response Headers, I see this:</p>
  
  <pre><code>Expires Wed, 15 Jun 2011 18:11:55 GMT
  Cache-Control   no-store, no-cache, must-revalidate, post-check=0, pre-check=0
  Pragma  no-cache
  </code></pre>
  
  <p>Which obviously explains the problem.</p>
  
  <p>Now, I've looked all over the code base, and it doesn't say "pragma" anywhere. .htaccess doesn't seem to have anything related either.</p>
  
  <p>Any ideas what could be setting those "pragma" (and "cache-control") headers, and how can I avoid it?</p>