<?php
function phptemplate_settings_custom($form, $settings) {
  // Theme width
  $form['tnt_container']['general_settings']['theme_width_config'] = array(
    '#type' => 'fieldset',
    '#title' => t('Theme width'),
    '#collapsible' => TRUE,
    '#collapsed' => TRUE,
  );
  $form['tnt_container']['general_settings']['theme_width_config']['theme_width'] = array(
    '#type'          => 'radios',
    '#title'         => t('Should the theme width be fixed or flexible?'),
    '#default_value' => $settings['theme_width'] ? $settings['theme_width'] : 'fixed',
    '#options'       => array(
      'fixed' => t('Fixed'),
      'flexible' => t('Flexible'),
    ),
  );
  return $form;
}