function valid_url($url)
    {
        $pattern = "/^((ht|f)tp(s?)\:\/\/|~/|/)?([w]{2}([\w\-]+\.)+([\w]{2,5}))(:[\d]{1,5})?/";
        if (!preg_match($pattern, $url))
        {
            return FALSE;
        }

        return TRUE;
    }