使用PHP进行JWT“签名验证失败”

<?php 
use FirebaseJWTJWT;
require 'vendor/autoload.php';

require('config/Database.php');
$db = new Database;

$key = "helloworld";


//$jwt = JWT::encode($token,$key,'HS512');

$post = file_get_contents("php://input");
$postdata = json_decode($post);

if($postdata){

    $email = $postdata->email;
    $password = $postdata->password;

    $query = "SELECT * FROM users WHERE email = :email";
    $db->query($query);
    $db->bind(":email",$email);
    $rows = $db->resultset();

    if(password_verify($password,$rows[0]["hash"])){
        $rows[0]["Success"] = "Success";
        $token = array(
            "rows" => $rows
        );
        $jwt = JWT::encode($token,'HS256');
        header("auth: " . $jwt);
        echo json_encode($jwt,128);
    }else{
        echo "Failed";
    }
}


?>

然后我正在解码此文件中的令牌

<?php 

use FirebaseJWTJWT;
require 'vendor/autoload.php';

require('config/Database.php');
$db = new Database;

$key = "helloworld";


//$jwt = JWT::encode($token,'HS512');

$post = file_get_contents("php://input");
$postdata = json_decode($post);


if($postdata){
    $userData = $postdata->userdata;
    // check if token is same stored in the database then decode
    $jwt = JWT::decode($userData,array('HS256'));

    echo $jwt;
}
?>

它失败,返回“签名验证失败”错误.
任何帮助表示赞赏.谢谢.