使用 Paypal 登录 API

Problem two is that when I generate the appropriate code using the Paypal PHP core sdk, it pops up a screen that does nothing. Code sample below:

<?php
$sdklib="sdk-core-php-master/lib";
require_once("$sdklib/PPConfigManager.php");
require_once("$sdklib/PPConstants.php");
require_once("$sdklib/common/PPApiContext.php");
require_once("$sdklib/auth/openid/PPOpenIdSession.php");

$apicontext = new PPApiContext(array('mode' => 'sandbox'));
$clientId = "AaggjRACLgNPQNEF83qQchE8_KzyKS4mCxmeaTDHTPSFp4hsGlAx4KPMqfZP";
$scope = array('openid', 'email'); 
$redirectUri = 'http://uc.mithril.com.au/testloginreturn.php';
$openidurl = PPOpenIdSession::getAuthorizationUrl($redirectUri, $scope , $clientId,  $apicontext); 

echo "<a href="$openidurl">Login Here</a>";
?>

再次点击显示的链接会产生一个空白屏幕.是不是我遗漏了一些明显的步骤，或者沙箱现在无法正常工作?