public static function sendHeaders()
{
if (self::$_headersSent) {
//throw new Exception('headers already sent');
return;
}
if (self::$_lastModified !== null) {
header('Last-Modified: ' . gmdate("D, d M Y H:i:s T", self::$_lastModified));
//header('X-Last-Modified: '.gmdate("D, d M Y H:i:s T", self::$_lastModified));
$ifModifiedSince = request::getHttpHeader('If-Modified-Since', false);
if ($ifModifiedSince) {
if ($ifModifiedSince == gmdate('D, d M Y H:i:s T', self::$_lastModified)) {
self::notModified();
}
}
}
self::$_headersSent = true;
}