[NativePHP]Google認証をfirebase無しで実装する

session_start();
session_regenerate_id(true);

$stateHash = hash('sha256', 'rundomstring');
$nonceHash = hash('sha256', 'rundomstring2');

$_SESSION['google_state'] = $stateHash;
$_SESSION['google_nonce'] = $nonceHash;

$authUrl = 'https://accounts.google.com/o/oauth2/auth';
$params = array(
  'client_id' => '~.apps.googleusercontent.com',
  'redirect_uri' => 'http://localhost:8888/~',
  'scope' => 'profile email',
  'response_type' => 'code',
  'access_type' => 'offline',
  'state' => $stateHash, //CSRF対策。SESSIONにも保存しておき、コールバック先で同じか判定。
  'nonce' => $nonceHash //number of once. IDトークンのレスポンスと比較後、削除。
);
header('Location: https://accounts.google.com/o/oauth2/auth?' . http_build_query($params));

  session_start();
  session_regenerate_id(true);

  //state検証
  $state = $_GET['state'];
  if($state != $_SESSION['google_state'])
  {
    echo '認証エラー';
    exit;
  }
  else
    unset($_SESSION['google_state']);

  $params = array(
    'code' => $_GET['code'],
    'grant_type' => 'authorization_code',
    'redirect_uri' => 'http://localhost:8888/~',
    'client_id' => '~.apps.googleusercontent.com',
    'client_secret' => 'クライアントシークレットをコピペ',
  );

  $options = array('http' => array(
    'method' => 'POST',
    'header' => array('Content-Type: application/x-www-form-urlencoded'),
    'content' => http_build_query($params)
  ));
  $resFromToken = file_get_contents('https://accounts.google.com/o/oauth2/token', false, stream_context_create($options));
  $token = json_decode($resFromToken, true);
  if (isset($token['error'])) {
      echo '認証エラー';
      exit;
  }
  $jwt = explode('.',$token['id_token']);
  $payload = json_decode(base64_decode($jwt[1]), true);
  //nonce検証
  $nonce = $payload['nonce'];
  if($nonce != $_SESSION['google_nonce'])
  {
    echo '認証エラー';
    exit;
  }
  else
    unset($_SESSION['google_nonce']);

  $accessToken = $token['access_token'];
  $params = array('access_token' => $accessToken);
  $resFromUserInfo = file_get_contents('https://www.googleapis.com/oauth2/v1/userinfo?' . http_build_query($params));
  $userInfo = json_decode($resFromUserInfo, true);
  var_dump($userInfo);
  //それぞれ取得する場合
  echo $userInfo["email"];
  echo $userInfo["name"];