我能'；t在解析PHP SDK中启动会话

在这个框架中启动会话时遇到问题。“登录”工作正常：

<?php require_once ('vendor/autoload.php'); ?>

<?php   
    use Parse\ParseObject;
    use Parse\ParseQuery;
    use Parse\ParseACL;
    use Parse\ParseUser;
    use Parse\ParseClient;
    use Parse\ParseException;
    use Parse\ParseFile;
    use Parse\ParseSessionStorage;

    session_start();

    ParseClient::initialize( "D4tClbuaS3OCWzRvQjT2L3vB8KUDJesFvVNbeJke", "P0eODP9cPcFFXOwokl1SRpUbSSjQx1kjO55S1nQ8", "lxmB0b8RhwNa0kneye4qHIEuiZDJR5B4cR8f82Ud" );
    // Set individual access rights

      // Login

     $usuario           = filter_var($_POST["usuariolog"], FILTER_SANITIZE_STRING);
    $password          = filter_var($_POST["passwordlog"], FILTER_SANITIZE_STRING);

    try {
        $user = ParseUser::logIn($usuario, $password);
    } catch(ParseException $ex) {
        echo 'Failed to create new object, with error message: ' . $ex-

    >getMessage();
        }

您收到了什么错误消息（如果有），或者更详细地描述了问题所在，以便我们提供帮助。您收到了什么错误消息（如果有），或者更详细地描述了问题所在，以便我们提供帮助。
<?php require_once ('vendor/autoload.php'); ?>

<?php   
    use Parse\ParseObject;
    use Parse\ParseQuery;
    use Parse\ParseACL;
    use Parse\ParseUser;
    use Parse\ParseClient;
    use Parse\ParseException;
    use Parse\ParseFile;
    ParseClient::initialize( "D4tClbuaS3OCWzRvQjT2L3vB8KUDJesFvVNbeJke", "P0eODP9cPcFFXOwokl1SRpUbSSjQx1kjO55S1nQ8", "lxmB0b8RhwNa0kneye4qHIEuiZDJR5B4cR8f82Ud" );
?>
    <?php session_start(); ?>

    $currentUser = ParseUser::getCurrentUser();
echo $currentUser;
if ($currentUser) { ?>
      It's ok
<?php
echo "username: ". $currentUser->getObjectId();
} else {
// show the signup or login page
echo "Not Found";
}
?>