public function setTelephone($telephone)
    {
        /**
         * Hack to support leading + sign
         * @see \luya\cms\models\NavItemPageBlockItem::rules()
         * @link https://github.com/luyadev/luya/pull/1815
         */
        $telephone = ltrim($telephone, '\\');

        $validator = new RegularExpressionValidator([
            'pattern' => '#^(?:0|\+[0-9]{2})[\d\- ()]+$#'
        ]);
        if ($validator->validate($telephone, $error)) {
            $this->_telephone = $telephone;
        } else {
            $this->_telephone = false;
        }
    }