PHP SESSION失效有关问题 !

var xmlhttp;
            if (window.XMLHttpRequest)
            {// code for IE7+, Firefox, Chrome, Opera, Safari
              xmlhttp=new XMLHttpRequest();
            }
            else
            {// code for IE6, IE5
              xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
            }
            xmlhttp.onreadystatechange=function()
              {
              if (xmlhttp.readyState==4 && xmlhttp.status==200)
                {
                        document.getElementById("myDiv").innerHTML=xmlhttp.responseText;
                }
              } 

             
            if(QC.Login.check())/*QQ 登录*/
            {
                    
                    QC.Login.getMe(function(openId, accessToken){
                            xmlhttp.open("GET","http://localhost/CI/index.php/SaveInfo/save_qq_openId?openId="+openId+"&accessToken="+accessToken,true);
                            xmlhttp.send();
                    });                        
            }