button_split_box
Github

    public function button_split_box()
    {
        return _class('html')->button_split_box('input_name', ['k1' => 'key1', 'k2' => 'key2']);
    }
    public function button_split_box($name, $values = [], $selected = '', $extra = [])
    {
        $extra['button_split'] = true;
        return $this->button_box($name, $values, $selected, $extra);
    }