It's concise, but a little bit long and kind of hard to read too. I thinks it's better to not save on lines here:
```php
if ($twigElement instanceof Twig_SimpleFunction || $twigElement instanceof Twig_SimpleFilter) {
    $this->_twig->{'add'.$classType}($twigElement);
} else {
    $this->_twig->{'add'.$classType}($name, $twigElement);
}
```