如何使用PHP在Facebook应用程序中获取用户电子邮件ID？

composer require facebook/graph-sdk

require_once 'vendor/autoload.php';

$app_id = 'your_app_id';
$app_secret = 'your_app_secret';

$redirect_uri = 'your_redirect_uri';

$fb = new \Facebook\Facebook([
  'app_id' => $app_id,
  'app_secret' => $app_secret,
  'default_graph_version' => 'v12.0',
]);

$helper = $fb->getRedirectLoginHelper();

$permissions = ['email']; // Optional permissions
$loginUrl = $helper->getLoginUrl($redirect_uri, $permissions);

try {
  $accessToken = $helper->getAccessToken();
} catch(Facebook\Exceptions\FacebookResponseException $e) {
  // When Graph returns an error
  echo 'Graph returned an error: ' . $e->getMessage();
  exit;
} catch(Facebook\Exceptions\FacebookSDKException $e) {
  // When validation fails or other local issues
  echo 'Facebook SDK returned an error: ' . $e->getMessage();
  exit;
}

if (! isset($accessToken)) {
  if ($helper->getError()) {
    header('HTTP/1.0 401 Unauthorized');
    echo "Error: " . $helper->getError() . "\n";
    echo "Error Code: " . $helper->getErrorCode() . "\n";
    echo "Error Reason: " . $helper->getErrorReason() . "\n";
    echo "Error Description: " . $helper->getErrorDescription() . "\n";
  } else {
    header('HTTP/1.0 400 Bad Request');
    echo 'Bad request';
  }
  exit;
}

try {
  $response = $fb->get('/me?fields=email', $accessToken->getValue());
} catch(Facebook\Exceptions\FacebookResponseException $e) {
  echo 'Graph returned an error: ' . $e->getMessage();
  exit;
} catch(Facebook\Exceptions\FacebookSDKException $e) {
  echo 'Facebook SDK returned an error: ' . $e->getMessage();
  exit;
}

$user = $response->getGraphUser();

echo 'Email: ' . $user['email'];