How do I check the logged-in user username/password/role using a function to validate them?

Question

I am allowing users to register an account on my site. They get a specific role using user_save().

When they log in for the first time, I have to verify the login credentials.

Is there a function to verify the login credentials?
Is there a function to get the user roles?

Answer 1

To check login credentials in Drupal 6&7:

$uid = user_authenticate($username, $password);

In Drupal 8:

// Inject user.auth service..
$uid = $this->userAuth->authenticate($username, $password);
// or
$uid = \Drupal::service('user.auth')->authenticate($username, $password);

To check roles:

/**
 * Check User roles
 * @param $role
 * @param null $user
 * @return bool
 */
function user_has_role($roles, $user = NULL) {
  if ($user == NULL) {
    global $user;
  }
  if (!is_array($roles)) {
    $roles = array($roles);
  }
  if (count(array_intersect($roles, $user->roles))) {
    return TRUE;
  }
  return FALSE;
}

Answer 2

$username = 'Username';
$pass = 'Password';

$uid = user_authenticate($username, $pass);

user_login_submit(array(), $uid); 
$load_user = user_load($uid);

if (in_array('role_name', $load_user->roles)) {
  // Add functionality that you want to do like if you want to redirect or anything else
}