Missing Array Key with apache_request_headers()

Hello, I don't get this at all. I'm trying to use php to manipulate my HTTP headers. [ Background Info about HTTP headers.] [ If an "ETag" header is sent by the server, then, next time a user-agent requests the same page, it sends back that header's value - in an "If-None-Match" header. ] The problem comes when I try to access the "If-None-Match" header using "apache_request_headers()". With Mozilla (I'm using 1.6b) the "If-Modified-Since" header is in the array. With Internet Explorer 6, it isn't, even though the header is sent out. (I'm checking the header output with the Proxomitron). Why is this happening and what can I do about it? Here are all the details: ------------------------------------------- The page I'm testing this with: <?php header("ETag: asdfghjkl"); $headers = apache_request_headers(); print_r(array_keys($headers)); exit; ?> ----------------------------------------- The Mozilla output on reload: Array ( [0] => Accept [1] => Accept-Charset [2] => Accept-Encoding [3] => Accept-Language [4] => Cache-Control [5] => Connection [6] => Host [7] => If-None-Match [8] => Keep-Alive [9] => User-Agent ) and from the Prox: GET /test.php HTTP/1.1 Host: pc User-Agent: Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.6b) Gecko/20031208 Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,image/jpeg,image/gif;q=0.2,*/*;q=0.1 Accept-Language: en-us,en;q=0.5 Accept-Encoding: gzip,deflate Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7 Keep-Alive: 300 If-None-Match: asdfghjkl Cache-Control: max-age=0 Connection: keep-alive ------------------------------------------- The IE6 output on reload is: Array ( [0] => Accept [1] => Accept-Encoding [2] => Accept-Language [3] => Connection [4] => Host [5] => Pragma [6] => User-Agent ) and from the Prox: GET /test.php HTTP/1.1 Accept: */* Accept-Language: en Accept-Encoding: gzip, deflate If-None-Match: asdfghjkl User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows 98) Host: pc Pragma: no-cache Connection: keep-alive -------------------------------------------- As you can see, in both cases, all the request headers shown by the Proxomitron are also in the array - with the exception, for IE6, of the "If-None-Match" header. Thanks in advance for your responses, Philip Pawley