public function hidden($var, $id = '')
{
$val = isset($this->options[$var]) ? $this->options[$var] : '';
if (is_bool($val)) {
$val = $val === true ? 'true' : 'false';
}
if ('' === $id) {
$id = 'hidden_' . $var;
}
echo '<input type="hidden" id="' . esc_attr($id) . '" name="' . esc_attr($this->option_name) . '[' . esc_attr($var) . ']" value="' . esc_attr($val) . '"/>';
}