browser detection and sending var to PHP

Hi, I'm trying to wite a javascript that will detect the browser/OS and then give that var to PHP. Could someone please float me some help? Here is what I have so far:

<script language="JavaScript">
<!--
function checkBrowser(NSvers,NSpass,NSnoPass,IEvers,IEpass,IEnoPass,OBpass) { //v4.0
var verStr=navigator.appVersion, app=navigator.appName, version = parseFloat(verStr), bSer;
if (app.indexOf('Netscape') != -1) {
if (version >= NSvers) {
bSer='NS4';} else {
bSer='old';}
} else if (app.indexOf('Microsoft') != -1) {
if (version >= IEvers | | verStr.indexOf(IEvers) != -1)
{ bSer='IE4';}
else{ bSer='old';}
} else if (OBpass>0){bSer='O';
}
if (bSer){ document.brow = bSer;}

//-->
</script>

Why use Javascript at all? That just complicates things. PHP can handle browser sniffing all on its own. Ask this question in the PHP forum, or better yet, see the manual at www.php.net/manual/

Besides, you can't really 'give' a variable to PHP once the page has loaded, so you would have to do some sort of page refresh, or popup window if you want to use Javascript.