循环时pdo的PHP错误

Question

您好我正在尝试使用带有php的pdo从数据库设置用户信息的缓存，但它会抛出一些错误

代码：

public function setUserCache($db)
    {
        if (!isset($_SESSION['user']['id']))
            exit();

        $statement = $db->prepare("SELECT * FROM users WHERE mail = :mail");
        $statement->execute(array(':mail' => $_SESSION['user']['username']));
        $userData = $statement->fetch(PDO::FETCH_ASSOC);


        $statement = $db->prepare("SELECT * FROM data WHERE id = :id");
        $statement->execute(array(':id' => $userData['id']));
        $roleplayDate = $statement->fetch(PDO::FETCH_ASSOC);

        while (list($var, $val) = each($userData)) {
            $_SESSION['user'][$var] = $val;
        }

        while (list($var, $val) = each($roleplayDate[0])) {
            $_SESSION['user'][$var] = $val;
        }
    }

错误：

E_WARNING Error in file »class.user.php« at line 101: Variable passed to each() is not an array or object

第101行：

while (list($var, $val) = each($roleplayDate[0])) {

循环时BOTH发生错误。