facebook访问令牌格式不正确

在阅读了stackoverflow上的所有教程和问题后，我仍然无法正常工作代码：

<?php
include_once 'debug/debug.php';
if (isset($_GET["username"])) {
    $appId="XXX";
    $appSecret="YYY";
    $code = $_GET["code"];
    echo "Code: <br>" . $code . "<hr>";
    //Optain App Token!    
    $ch = curl_init ();
    curl_setopt ( $ch, CURLOPT_URL,
        "https://graph.facebook.com/oauth/access_token?client_id=" . $appId .
        "&client_secret=". $appSecret. 
        "&grant_type=client_credentials");
    curl_setopt ( $ch, CURLOPT_RETURNTRANSFER, 1); 
    $result = curl_exec($ch);
    curl_close($ch); 
    $access_token = explode("=", $result)[1];
    echo $access_token;
    //Option further Information
    $ch = curl_init ();
    //curl_setopt ( $ch, CURLOPT_URL, "https://graph.facebook.com/me?access_token=" . $code);
    curl_setopt ( $ch, CURLOPT_URL, "https://graph.facebook.com/debug_token?input_token=" . $code . "&access_token=" . $access_token);
    curl_setopt ( $ch, CURLOPT_RETURNTRANSFER, 1); 
    $result = curl_exec($ch);
    curl_close($ch); 
    echo $result;
}
?>

答案是：
｛"data"：｛"error"：｛｛"message"："访问令牌AQB6hhoeZJ1SR5RqtPp-ied1Fg38GV95tW2YrVR9EfK6Y8H7QgcrSr8uageIpKa4rPI7z4qSw45COZZL1XMDUuigsrBLNg5NKXl2bd9GPYC1Qo5peH81mGqP6LqK-orL3uKCH3Ta3kHOGp76RmK8p391soS47ZR8WE5gNx6s35qctgoHuWE47R0w93GeNglRxu2UtsGhZgyGiA9l12Bl Mq9NX5O9Kcp2DupVqWs67Vnqz8MntrTx-AzbFhdHrYtWOhmFb8WybrT3ZuGqETZEAGc9JOTuhiHJW3Elp_rE7IWA50MIWsAaqM77fuI1Go"，"代码"：190｝，"is_valid"：false｝｝
$代码是通过从facebook登录并调用此uri来提供的：
https://www.facebook.com/dialog/oauth?client_id=APP_ID&重定向uri=http://www.mineforce.de/ms/fblogin.php?username=USERNAME
我不明白为什么访问令牌应该是错误的，因为我们是通过facebook自己获得的
印刷品等可在此处找到：
http://www.mineforce.de/ms/fblogin.php?username=phibedy&代码=AQB6hhoeZJ1SR5RqtPp-ied1Fg38GV95tW2YrVR9EfK6Y8H7QgcrSr8uageIpKa4rPI7z4qSw45COZZL1XMDUuigsrBLNg5NKXl2bd9GPYC1Qo5peH81mGqP6LqK或L3uKCH3Ta3kHOGp76RmK8p391soS47ZR8WE5gNx6s35qctgoHuWE47R0w93GeNglRxu2UtVsGhZgyGiA9l12Bq9NX5O9Kcp2DupVqWs67Vnq z8MntrTx-AzbFhdHrYtWOhmFb8WybrT3ZuGqETZEAGc9JOTuhiHJW3Elp_rE7IWA50MIWsAaqM77fuI1Go#=

其次，我不明白为什么fb把#=放在代币的末尾

干杯：）