Magento: Show Optgroup in select box

Here Furniture is OptGroup. Copy and paste in any PHTML file and check the output.

$options = array(0=>array('label' => 'Furniture',

                          'value' => array

                            (

                                0 => array

                                (

                                    'label' => 'Chair',

                                    'value' => 1

                                ),

                                1 => array

                                (

                                    'label' => 'Couch',

                                    'value' => 2

                                )

                            )

                        )

                    );

$tmp = Mage::app()->getLayout()->createBlock('core/html_select')

            ->setName('product_id')

            ->setId('product_id')

            ->setTitle('products')

            ->setClass('validate-select');

$select =  $tmp->setOptions($options);

echo $select->getHtml();