Opposite to theme_get_setting To Set In the template.php file, we grab the theme settings:

if(theme_get_setting('fix_sidebar')){
...
        variable_set('fixed_navbar',1);
    }


Based on the theme setting(i.e fix_sidbar'), we want to reset another theme setting(i.e fixed_navbar) as you see above. However, it does not appear to be working. It is not showing up theme settings that has:

 $form['style']['fixed_navbar'] = array(
        '#title' =&gt; t('Fixed Navbar'),
        '#default_value' =&gt; theme_get_setting('fixed_navbar'),
        '#type' =&gt; 'checkbox',
    );


How to do the opposite of theme_get_setting API to reset the setting with new value? Thank You
If I understand you correctly, you should be doing this

$form['style']['fixed_navbar'] = array(
    '#title' =&gt; t('Fixed Navbar'),
    '#default_value' =&gt; variable_get('fixed_navbar', 1),
    '#type' =&gt; 'checkbox',
);