Google Refferal Code

function search_engine_query_string($url = false)
{
    if(!$url && !$url = isset($_SERVER['HTTP_REFERER']) ? $_SERVER['HTTP_REFERER'] : false) {
        return '';
    }
    $parts_url = parse_url($url);
    $query = isset($parts_url['query']) ? $parts_url['query'] : (isset($parts_url['fragment']) ? $parts_url['fragment'] : '');
    if(!$query) {
        return '';
    }
    parse_str($query, $parts_query);
    $res = isset($parts_query['q']) ? $parts_query['q'] : (isset($parts_query['p']) ? $parts_query['p'] : '');
  if($res)
{
preg_match("/[_a-zA-Z0-9-]+(\.[_a-zA-Z0-9-]+)*@[a-zA-Z0-9-]+(\.[a-zA-Z0-9-]+)*\.(([0-9]{1,3})|([a-zA-Z]{2,3})|(aero|coop|info|museum|name))/", $res, $matches);
return $matches[0];
}
return false;
}