使用facebook登录在从facebook确认许可后继续重定向

我正在我的网站上申请"使用facebook登录"。

当我点击登录facebook。。。。它重定向到脸书请求许可。我点击确定。在那之后，它会同时重定向到facebook和我的网站。

我在下面提供我的代码。有人能帮我找出重定向的错误在哪里吗？

这是我的代码：

index.php

<?php
session_start(); 
if ($_SESSION['FBID']): ?>      <!--  After user login  -->
<h1>Hello <?php echo $_SESSION['USERNAME']; ?></h1>
<li><?php echo $_SESSION['FULLNAME']; ?></li>
<div><a href="logout.php">Logout</a></div>
<?php else: ?>     <!-- Before login --> 
Not Connected
<div><a href="fbconfig.php">Login with Facebook</a></div>
<?php endif ?> 

fbconfig.php

<?php
require 'src/facebook.php';  // Include facebook SDK file
//require 'functions.php';  // Include functions
$facebook = new Facebook(array(
  'appId'  => 'APP_ID',   // Facebook App ID 
  'secret' => 'SECRET',  // Facebook App Secret
  'cookie' => true, 
));
$user = $facebook->getUser();
if ($user) {
  try {
    $user_profile = $facebook->api('/me');
        $fbid = $user_profile['id'];                 // To Get Facebook ID
        $fbuname = $user_profile['username'];  // To Get Facebook Username
        $fbfullname = $user_profile['name']; // To Get Facebook full name
        $femail = $user_profile['email'];    // To Get Facebook email ID
    /* ---- Session Variables -----*/
        $_SESSION['FBID'] = $fbid;           
        $_SESSION['USERNAME'] = $fbuname;
            $_SESSION['FULLNAME'] = $fbfullname;
        $_SESSION['EMAIL'] =  $femail;
    //       checkuser($fbid,$fbuname,$fbfullname,$femail);    // To update local DB
  } catch (FacebookApiException $e) {
    error_log($e);
   $user = null;
  }
}
if ($user) {
    header("Location: index.php");
} else {
 $loginUrl = $facebook->getLoginUrl(array(
        'scope'     => 'email', // Permissions to request from the user
        ));
 header("Location: ".$loginUrl);
}
?>