Flarum\Core\User::register PHP Method

    public static function register($username, $email, $password)
    {
        $user = new static();
        $user->username = $username;
        $user->email = $email;
        $user->password = $password;
        $user->join_time = time();
        $user->raise(new UserWasRegistered($user));
        return $user;
    }

 /**
  * {@inheritdoc}
  */
 public function handle(ServerRequestInterface $request)
 {
     $body = $request->getParsedBody();
     $email = array_get($body, 'email');
     $username = array_get($body, 'username');
     $password = array_get($body, 'password');
     $user = User::register($username, $email, $password);
     $user->activate();
     if (isset($token)) {
         foreach ($token->payload as $k => $v) {
             $user->{$k} = $v;
         }
     }
     $user->create_from = '来自社区账号系统';
     $user->save();
     return new JsonResponse(['userId' => $user->id]);
 }