public static function validateURL($url = null)
    {
        $url = trim($url);

        if (is_null($url) || $url == '') {
            return $url;
        }

        if (!preg_match('#^http[s]?:\/\/#i', $url)) {
            $url = 'http://' . $url;
        }

        include TOOLKIT . '/util.validators.php';

        if (!preg_match($validators['URI'], $url)) {
            $url = '';
        }

        return $url;
    }