Livezilla - 会话之间总是相同的访问者

Question

I have a Livezilla instalation where I have the following problem. If USER X logs in one browser, and sends a chat message to an operator it shows as as USER X. But, after USER X logging off and USER Y logs in using the same browser, and send a chat message to the operator, it will show as being USER X instead of USER Y.

Here's what I'm doing:

<script type="text/javascript">
var lz_data = {overwrite:false,111:'<?php echo $_SESSION["username"]; ?>', language:'<?php echo $_SESSION['userlang']; ?>'};
</script>
<script type="text/javascript" id="a739c86be11f7d549fc15891d95e3fe8" src="www.my-livezilla-domain.com/script.php?id=a739c86be11f7d549fc15891d95e3fe8" defer></script>

Anyone has any insight to what I could be doing wrong? Do you need me to provide more information?

Thanks in advance.