I cannot set new Session in OJS

Software Support
1

I am developing an OJS plugin.
I want to set a session variable.
I set the session in a class like Article class:

$sessionManager =& SessionManager->getManager();
$session =& $sessionManager->getUserSession();
$session->setSessionVar(’$x’, $x);

but, I cannot get the variable $x in other class like submission class

$sessionManager =& SessionManager->getManager();
$session =& $sessionManager->getUserSession();
$x = $session->getSessionVar(’$x’);

what is the problem?