Drupal: How to differentiate between new user registration and user password update in hook_user validate operation?

I am using hook_user validate operation 开发者_如何学Cto validate user registration info against my business logic.

I want separate logics to run on registration and change password.

But I am unable to differentiate between the two - both pass through validation and same code is run for both.

How can I differentiate between the two inside the validate op in hook_user?

with $form_id

if ( ($form_id == 'user_profile_form' && arg(3) == NULL) {

  // validation code for updating 

}

elseif ($form_id == 'user_register') ) {

 // validation code for registering

}

In Drupal 7 you may try something like:

/**
 * Implements hook_form_FORM_ID_alter().
 * Form ID: user_profile_form
 */
function foo_form_user_profile_form_alter($form, &$form_state) {
  // Set a custom form validate and submit handlers.
  $form['#validate'][] = 'foo_form_user_profile_form_validate';
  $form['#submit'][] = 'foo_form_user_profile_form_submit';
}

/**
 * Implements hook_form_FORM_ID_alter().
 * Form ID: user_register_form
 */
function foo_form_user_register_form_alter($form, &$form_state) {
  if ($form['#user_category'] == 'account') {
    // Set a custom form validate and submit handlers.
    $form['#validate'][] = 'foo_form_user_register_validate';
    $form['#submit'][] = 'foo_form_user_register_submit';
  }
}