WPDKUser::nice_name PHP Method

    public static function nice_name($firstName, $lastName)
    {
        $result = '';
        if (empty($firstName) && empty($lastName)) {
            return $result;
        }
        if (empty($firstName)) {
            return $lastName;
        }
        if (empty($lastName)) {
            return $firstName;
        }
        $result = sprintf('%s.%s', strtoupper(substr($firstName, 0, 1)), ucfirst($lastName));
        return $result;
    }

 /**
  * Create a WordPress user and return the user id on success, WP_Error otherwise.
  *
  * @deprecated since 1.7.3 - Use `createWithArgs` instead
  *
  * @param string      $first_name First name
  * @param string      $last_name  Last name
  * @param string      $email      Email address
  * @param bool|string $password   Optional. Clear password, if set to FALSE a random password is created
  * @param bool        $enabled    Optional. If FALSE the WPDK user status is set to disable. Default FALSE.
  * @param string      $role       Optional. User role, default 'subscriber'
  *
  * @return int|WP_Error
  */
 public function create($first_name, $last_name, $email, $password = false, $enabled = false, $role = 'subscriber')
 {
     // For security reason an user must have a password
     if (false === $password) {
         $password = wp_generate_password(20, false);
         /**
          * Fires when a random password is generated.
          *
          * @param string $password Random Password.
          */
         do_action('wpdk_users_random_password', $password);
     }
     $nice_name = WPDKUser::nice_name($first_name, $last_name);
     $display_name = WPDKUser::full_name($first_name, $last_name);
     $user_data = array('user_login' => $email, 'user_pass' => $password, 'user_email' => $email, 'user_nicename' => $nice_name, 'nickname' => $nice_name, 'display_name' => $display_name, 'first_name' => $first_name, 'last_name' => $last_name, 'role' => $role);
     $user_id = wp_insert_user($user_data);
     if (is_wp_error($user_id)) {
         return $user_id;
     }
     // Store IP Address
     if (isset($_SERVER['REMOTE_ADDR']) && !empty($_SERVER['REMOTE_ADDR'])) {
         update_user_meta($user_id, WPDKUserMeta::REMOTE_ADDR, $_SERVER['REMOTE_ADDR']);
     }
     // Disable user if required
     if (false === $enabled) {
         /**
          * Filter the user status before update.
          *
          * @param string $status  The status id. Default `WPDKUserStatus::DISABLED`.
          * @param int    $user_id The user id.
          */
         $status = apply_filters('wpdk_users_status', WPDKUserStatus::DISABLED, $user_id);
         update_user_meta($user_id, WPDKUserMeta::STATUS, $status);
         /**
          * Filter the user status description.
          *
          * @param string $description User stats description.
          * @param int    $user_id     The user id.
          */
         $status_description = apply_filters('wpdk_users_status_description', '', $user_id);
         update_user_meta($user_id, WPDKUserMeta::STATUS_DESCRIPTION, $status_description);
     }
     return $user_id;
 }