/**
* Checks if content has changed by the etag cachekey.
*
* HTTP_IF_NONE_MATCH feature
*
* @param string $cacheKey HTTP Cachekey to identify the cache
*/
public static function sendEtag($cacheKey)
{
// Laut HTTP Spec muss der Etag in " sein
$cacheKey = '"' . $cacheKey . '"';
// Sende CacheKey als ETag
header('ETag: ' . $cacheKey);
// CacheKey gefunden
// => den Browser anweisen, den Cache zu verwenden
if (isset($_SERVER['HTTP_IF_NONE_MATCH']) && $_SERVER['HTTP_IF_NONE_MATCH'] == $cacheKey) {
self::cleanOutputBuffers();
header('HTTP/1.1 ' . self::HTTP_NOT_MODIFIED);
exit;
}
self::$sentEtag = true;
}
