Elgg\Security\UrlSigner::sign PHP Method

    public function sign($url, $expires = false)
    {
        $url = elgg_normalize_url($url);
        $parts = parse_url($url);
        if (isset($parts['query'])) {
            $query = elgg_parse_str($parts['query']);
        } else {
            $query = [];
        }
        if (isset($query[self::KEY_MAC])) {
            throw new \InvalidArgumentException('URL has already been signed');
        }
        if ($expires) {
            $query[self::KEY_EXPIRES] = strtotime($expires);
        }
        ksort($query);
        $parts['query'] = http_build_query($query);
        $url = elgg_http_build_url($parts, false);
        $token = elgg_build_hmac($url)->getToken();
        return elgg_http_add_url_query_elements($url, [self::KEY_MAC => $token]);
    }