如果已经设置了Facebook api，则禁止其向DB添加电子邮件

我有一个登录系统，允许用户使用Facebook的api注册或登录。

我添加了一些代码来检查是否存在与Facebook电子邮件匹配的电子邮件，如果存在，请将Facebook id添加到数据库中的那一行。

我的帐户设置中还有一个选项，允许用户更改他们的电子邮件地址。

我遇到的问题是，如果用户在获得Facebook id后更改了他们的电子邮件地址，下次用户注销并返回我的网站时，他们的电子邮件会更新为他们Facebook帐户上的电子邮件。

我仍然希望允许User:：createOrUpdateGraphNode($facebook_User(只在不存在电子邮件的情况下向我的数据库添加电子邮件，因此是为了新用户。

但如果电子邮件已经存在，则不会。这样，如果用户确实更改了他们的电子邮件，登录Facebook不会影响它。

我知道我可以从中删除

protected static 
    $graph_node_field_aliases = [
            'id' => 'facebook_id',
            // 'name' => 'name',
            //'email' => 'email',
        ];

但是当新用户注册时，它不会在我的数据库中添加电子邮件。

这个函数中的一切都在进行：createOrUpdateGraphNode($facebook_user)所以我不知道如何添加一个if，比如：

if($user->facebook_id == facebook_id && $user->email) { 
  do something 
}

我在用sammyklavel/facebooksdkhttps://github.com/SammyK/LaravelFacebookSdk

Facebook回调如下：

function facebookCallBack(LaravelFacebookSdk $fb) {
    // Obtain an access token.
try {
    $token = $fb->getAccessTokenFromRedirect();
} catch (Facebook'Exceptions'FacebookSDKException $e) {
    dd($e->getMessage());
}
// Access token will be null if the user denied the request
// or if someone just hit this URL outside of the OAuth flow.
if (! $token) {
    // Get the redirect helper
    $helper = $fb->getRedirectLoginHelper();
    if (! $helper->getError()) {
        abort(403, 'Unauthorized action.');
    }
    // User denied the request
    dd(
        $helper->getError(),
        $helper->getErrorCode(),
        $helper->getErrorReason(),
        $helper->getErrorDescription()
    );
}
if (! $token->isLongLived()) {
    // OAuth 2.0 client handler
    $oauth_client = $fb->getOAuth2Client();
    // Extend the access token.
    try {
        $token = $oauth_client->getLongLivedAccessToken($token);
    } catch (Facebook'Exceptions'FacebookSDKException $e) {
        dd($e->getMessage());
    }
}
$fb->setDefaultAccessToken($token);
// Save for later
Session::put('fb_user_access_token', (string) $token);
// Get basic info on the user from Facebook.
try {
    $response = $fb->get('/me?fields=id,name,email');
} catch (Facebook'Exceptions'FacebookSDKException $e) {
    dd($e->getMessage());
}
// Convert the response to a `Facebook/GraphNodes/GraphUser` collection
$facebook_user = $response->getGraphUser();
// dd($facebook_user['email'] );

// Create the user if it does not exist or update the existing entry.
// This will only work if you've added the SyncableGraphNodeTrait to your User model.
$user = User::where('email', $facebook_user['email'])->first();
if(isset($user)) {
    // // Convert the response to a `Facebook/GraphNodes/GraphUser` collection
    $facebook_user = $response->getGraphUser();
    $current_user = $user;
    $current_user->facebook_id = $facebook_user['id'];
    $current_user->save();
} else {
$user = User::createOrUpdateGraphNode($facebook_user);
}
// Log the user into Laravel
Auth::login($user);
if (Auth::user()->terms && Auth::user()->active) {
    return redirect()->route('home');
}
$active = 1;
Auth::user()->update([
    'active' => $active,
]);
return redirect()->route('auth.signupdetails');
}

if($user = User::where('email', $facebook_user['email'])->where('active', true)->first()) {
    // // Convert the response to a `Facebook/GraphNodes/GraphUser` collection
    $facebook_user = $response->getGraphUser();
    $current_user = $user;
    $current_user->facebook_id = $facebook_user['id'];
    $current_user->save();
} // if facebook id exist in databse, just update
elseif ($user = User::where('facebook_id', $facebook_user['id'])->first()) {
    $facebook_user = $response->getGraphUser();
    $current_user = $user;
    $current_user->facebook_id = $facebook_user['id'];
    $current_user->save();
} // if user facebook id and no email matching facebook's email is in the database, create new user
else {
    $facebook_user = $response->getGraphUser();
     $user = User::create([
        'email' => $facebook_user['email'],
        'facebook_id' => $facebook_user['id'],
    ]);
}
// Log the user into Laravel
Auth::login($user);