How can I pass a PHP variable to javascript?

[Sploosh]

I want to use a PHP variable as a javascript variable - specifically I want to user the PHP variable session_id(); and use this as a javascript variable. \[code\]<?php$php_var = session_id();?><script language="JavaScript" type="text/javascript">js_var = <?php echo($php_var ?>;</script>\[/code\]This seems like it should work for me but it doesnt can anyone suggest a better way?