form_callback.php

/**
 * Privacy settings form for user.
 */
function privacy_settings_form_callback($form, &$form_state) {
  global $user;
  $form = array();
  $options = array(0 => 'Public', 1 => 'Friends', 2 => 'Private');
  $instances = field_info_instances('user', 'user');
  foreach ($instances as $field_name => $field_info) {
    $form[$field_name] = array(
      '#type' => 'select',
      '#title' => t('Who can see your ') . $field_info['label'] . ' ?',
      '#options' => $options,
      '#default_value' => $user->data['privacy_settings'][$field_name],
    );
  }
  $form['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Save'),
  );
  return $form;
}