Topic: How to transfer the value of the option

Hi everyone, here are a normal SELECT and it option.
I have to take the value of the field and drag it to the option, but I do not know how

$opt['mix']      = array('2' => __('category 2', 'catalog'), 
                                  '2' => __('category 2', 'catalog'), 
                                  '3' => __('category 2', 'catalog'), 
                                  '4' => __('category 3', 'catalog'), 
                                  '5' => __('category 4', 'catalog'), 
                                  '6' => __('category 5', 'catalog'));
 $post['mix_1']   = (Request::post('catalog_mix_1'))       ? Request::post('catalog_mix_1')       : $data['mix_1'];