So I am sending a header in php to cache my page (this integrates into our "CDN" (contendo/akamai) as well). I always use this pragma: cache header, I've seen various examples use it as well; however, I just checked fiddler to test traffic for this .net application we developed and it says: 

Legacy Pragma Header is present: cache
!! Warning IE supports only an EXACT match of "Pragma: no-cache". IE will ignore the Pragma header if any other values are present.
...

I suppose that is ok. The rest of the response seems fine and to my specs. Here is my code:

function headers_for_page_cache($cache_length=600){
    $cache_expire_date = gmdate("D, d M Y H:i:s", time() + $cache_length);
    header("Expires: $cache_expire_date");
    header("Pragma: cache");
    header("Cache-Control: max-age=$cache_length");
    header("User-Cache-Control: max-age=$cache_length");
}

The question is does this matter? What does the pragma header even do? Do I need it? I checked the HTTP header spec documentation and it said it is implementation specific and the only Pragma that is enforced is "Pragma: no-cache".

Is this the best choice of headers to cache for a specific amount of time?

php caching http-headers
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