That is what I get for my browser.
Something like this would work well.
$langdone == false;
if (preg_match("/en-gb/siU", $_SERVER["HTTP_ACCEPT_LANGUAGE"]) == 1) {
 echo "echo your en gb links/banner";
 $langdone == true;
}
if (preg_match("/en-us/siU", $_SERVER["HTTP_ACCEPT_LANGUAGE"]) == 1) {
 echo "echo your en us links/banner";
 $langdone == true;
}// default
if ($langdone==false) {
 echo "echo your default links/banner";
}
?>
In php preg_match the s = treat as string, not exactly needed as there are no new lines, i = case insensitive and U = ungreedy