How to modify Drupal configuration programmatically?

Question

How can I modify the Drupal settings found on /admin/config/people/accounts (and other configuration pages) using a custom module?

For example, how do I rename the Anonymous user and change 'Who can register accounts' setting from 'administrator' to 'visitor' programmatically with a custom module?

Answer 1

Most of these configuration settings tend to be controlled by a variable, so Drupal uses variable_get() and variable_set() to retrieve and modify these values.

To find out the variable name and value you can have a look at the source page. For example:

<label for="edit-user-register">Who can register accounts? </label>
<div id="edit-user-register" class="form-radios">
  <input type="radio" id="edit-user-register-0" name="user_register" value="0" class="form-radio">  
  <label class="option" for="edit-user-register-0">Administrators only </label>

  <input type="radio" id="edit-user-register-1" name="user_register" value="1" class="form-radio">
  <label class="option" for="edit-user-register-1">Visitors </label>

  <input type="radio" id="edit-user-register-2" name="user_register" value="2" checked="checked" class="form-radio">
  <label class="option" for="edit-user-register-2">Visitors, but administrator approval is required </label>
</div>

Here you can see that in order to change the "Who can register accounts?" option, you need to change the value of the user_register variable. You can set it to 1 for visitors, so putting this code in your module will do the trick:

variable_set('user_register', 1);

Of course, this is if you're too lazy to open the source code :) . The other way is to find out which callback generates this form, and inspect user.module:

function user_menu() {
  //snip...
  $items['admin/config/people/accounts'] = array(
    'title' => 'Account settings',
    'description' => 'Configure default behavior of users, including registration requirements, e-mails, fields, and user pictures.',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('user_admin_settings'),
    'access arguments' => array('administer users'),
    'file' => 'user.admin.inc',
    'weight' => -10,
  );

Then find the callback function user_admin_settings() in user.admin.inc:

$form['registration_cancellation']['user_register'] = array(
  '#type' => 'radios', 
  '#title' => t('Who can register accounts?'), 
  '#default_value' => variable_get('user_register', USER_REGISTER_VISITORS_ADMINISTRATIVE_APPROVAL), 
  '#options' => array(
    USER_REGISTER_ADMINISTRATORS_ONLY => t('Administrators only'), 
    USER_REGISTER_VISITORS => t('Visitors'), 
    USER_REGISTER_VISITORS_ADMINISTRATIVE_APPROVAL => t('Visitors, but administrator approval is required'),
  ),
);

So there you have your variable and in fact there's some constant to set up the values: USER_REGISTER_VISITORS.