Error Message - Need help troubleshooting

Hello List.

I have some JS code that open a new window with a contact form in it.   
When the link is clicked to open the new window, I will get the  
following error SOMETIMES:

"Warning: Unknown: Your script possibly relies on a session side- 
effect which existed until PHP 4.2.3. Please be advised that the  
session extension does not consider global variables as a source of  
data, unless register_globals is enabled. You can disable this  
functionality and this warning by setting session.bug_compat_42 or  
session.bug_compat_warn to off, respectively. in Unknown on line 0"

My JS code with a bit of PHP in it looks like this:

function loadOSS()
var oss_itemid = "<?php echo $item_id; ?>";
var loadOSS = window.open("my_url/my_file.php?iid=" + oss_itemid, "",  
"scrollbars 
= 
no 
,menubar 
= 
no 
,height=600,width=600,resizable=yes,toolbar=no,location=no,status=no");
}

As I said above, the error message does not always appear.

Is the error due to the fact I am JS & PHP together?

Any help in understanding what I am doing wrong is appreciated.

  --Rick