Drupal 7 - Confirm email address - drupal

Question

I have added some extra fields to the standard 'create account' page; notably a 'confirm email' field.
How do hook into the validation so that I can add some custom validation rules of my own (e.g. to check the two emails match)?
I have found hook_user_presave, but am unsure on how to code it or where I should put it.
Any and all help appreciated.

Answer 1

I would advise installing the LoginToboggan module, it actually has the option for that exact functionality out of the box and has a bunch of other useful options as well.
If you want to do it yourself though you'd probably be better off implementing hook_form_FORM_ID_alter() and adding a validation function directly to the registration form:
function mymodule_form_user_register_form_alter(&$form, &$form_state, $form_id) {
$form['#validate'][] = 'mymodule_user_register_form_validate';
}
function mymodule_user_register_form_validate(&$form, &$form_state) {
if ($form_state['values']['first_email'] != $form_state['values']['second_email']) {
form_set_error('second_email', 'The email addresses much match.');
}
}
Make sure you clear Drupal's cache once you've implemented the form alter function so Drupal registers it correctly.
Hope that helps.

Answer 2

Here is the example solution for Drupal 7:
/**
* Implements hook_menu().
* Note: You can define your own menu callback optionally.
*/
function foo_menu() {
$items['foo-signup'] = array(
'title' => 'Create new account',
'page callback' => 'drupal_get_form',
'page arguments' => array('user_register_form'),
'access callback' => 'user_register_access',
'type' => MENU_CALLBACK,
);
return $items;
}
/**
* Implements hook_form_FORM_ID_alter().
*/
function foo_form_user_register_form_alter(&$form, &$form_state, $form_id) {
$form['account']['mail_confirm'] = array(
'#type' => 'textfield',
'#title' => t('Confirm e-mail address'),
'#maxlength' => EMAIL_MAX_LENGTH,
'#description' => t('Please confirm your e-mail address.'),
'#required' => TRUE,
);
$form['#validate'][] = 'foo_user_register_form_validate';
}
/**
* Implements validation callback.
*/
function foo_user_register_form_validate(&$form, &$form_state) {
if ($form_state['values']['mail'] != $form_state['values']['mail_confirm']) {
form_set_error('mail_confirm', 'The email addresses must match.');
}
}