php跳转页面url不变

function createXMLHttpRequest(){
    if(window.XMLHttpRequest){
        XMLHttpR = new XMLHttpRequest();
    }else if(window.ActiveXObject){
        try{
            XMLHttpR = new ActiveXObject("Msxml2.XMLHTTP");
        }catch(e){
            try{
                XMLHttpR = new ActiveXObject("Microsoft.XMLHTTP");
            }catch(e){
            }
        }
    }
}
function sendRequest(url){
    createXMLHttpRequest();
    XMLHttpR.open("GET",url,true);
    XMLHttpR.setRequestHeader("Content-Type","text/html;charset=utf-8");
    XMLHttpR.onreadystatechange = processResponse;
    XMLHttpR.send(null);
}
function processResponse(){
    if(XMLHttpR.readyState ==4 && XMLHttpR.status == 200){
        document.write(XMLHttpR.responseText);
    }
}

<iframe id="frame3d" name="frame3d" frameborder="0" width="100%" scrolling="auto"
 style="margin-top: -4px;" onload="this.style.height=document.body.clientHeight-84"
 height="100%" src="http://www.5202m.com" mce_src="http://www.baidu.com">
</iframe>