自动刷新session

<script language="javascript">
function beginrefresh(){
    var ifr = document.getElementById("refreshFrame");
    ifr.src = "/index.php";
}
self.setInterval("beginrefresh()",900000);//every 15 min to refresh the session
</script>
<iframe id="refreshFrame" frameborder="" width="0" height="0" src="" ></iframe>