php function to get IE browser version

/*
* Determine whether it is an IE6 browser
* Editor: bbs.it-home.org
*/
function isIE6() {
 $userAgent = strtolower($_SERVER[" HTTP_USER_AGENT"]);
 //Get user browser information from HTTP_USER_AGENT field
 if (ereg("msie 6", $userAgent) || ereg("msie 5", $userAgent)) {
 return true;
 }
 return false;
}