private function getCallbackUrl($callback_url)
    {
        $callback_url = $callback_url ?: $this->config_handler->get('laravel-facebook-sdk.default_redirect_uri');

        return $this->url->to($callback_url);
    }
private function getCallbackUrl($callback_url)
    {
        $callback_url = $callback_url ?: $this->config_handler->get('laravel-facebook-sdk.default_redirect_uri');

        return $this->url->to($callback_url);
    }
private function getCallbackUrl ( $ callback_url ) { $ callback_url = $ callback_url ? : $ this -> config_handler -> get ( 'laravel-facebook-sdk.default_redirect_uri' ) ; return $ this -> url -> to ( $ callback_url ) ; }
Get the fallback callback redirect URL if none provided.

@param string $callback_url

@return string
Get the fallback callback redirect URL if none provided .