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19 years ago
All versions of MSIE have a bug where they don't cache gzipd contents. If your application depends on caching, this is something to keep in mind. In the end, I did:

<?php

// These are so benificial, they default to true.
if (!isset($use_page_cache))
    $use_page_cache = 1;
if (!isset($use_compression))
    $use_compression = 1;

// Add browsers here as we must detect them. Opera is an oddball, if we don't detect
// it specifically, it will turn up as MSIE

$browser="other";
if (isset($_SERVER['HTTP_USER_AGENT'])) {
    $agent = $_SERVER['HTTP_USER_AGENT'];
    if (eregi("opera",$agent)){
    $browser="opera";
    }elseif(eregi("msie",$agent)){
    $browser="msie";
    }
}

if ($use_compression && !( $use_page_cache && $browser == "msie")) {
    // Turn on compression, makes quite a difference in bandwith usage.
    // However, MSIE (all versions) have a bug with compression and caching. So for MSIE
    // it's either compression or caching. We choose caching.
    ob_start('ob_gzhandler');
}

session_cache_limiter("must-revalidate");

session_start();

// ... put stuff in $content ...

if ($use_page_cache) {
    // MD5 is slow, however with a fast server (PIII or better) we should be OK
    $hash = md5($content);
    $headers = getallheaders();
    if (isset($headers['If-None-Match']) && ereg($hash, $headers['If-None-Match']))
    {
    header('HTTP/1.1 304 Not Modified');
    exit;
    }
    header("ETag: \"$hash\"");
}

print $content;

?>
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