how to get server response in PHP html5 upload

I got a part of html5 upload script, it is as follow:

        var xhr = new XMLHttpRequest();

        xhr.addEventListener("load", function () {
            alert('done');
            var i =xhr.getResponseHeader('header');
            alert(i.status);
   开发者_JAVA百科     }, false);

        xhr.open("post", "upload/process", true);

        xhr.setRequestHeader("Content-Type", "application/json-rpc");
        xhr.setRequestHeader("X-File-Name", file.fileName);
        xhr.setRequestHeader("X-File-Size", file.fileSize);
        xhr.setRequestHeader("X-File-Type", file.type);

        xhr.send(file);

And My PHP is as follow:

    $name = $_SERVER['HTTP_X_FILE_NAME'];
    $path = '/upload/';
    if(file_put_contents($path.$name, "php://input"))
    {
        echo json_encode(array('status'=>'sucess', 'name'=>$name)); 
    }else{
        echo json_encode(array('status'=>'error'));
    }

I want to grab the Json response from server and show it. So far I don't know how, I tried

var i =xhr.getResponseHeader('header');
alert(i.status);

But i got a error "NULL".

The MDC - XMLHttpRequest documentation provides good information.

The response is contained in xhr.responseText. So you have to do:

xhr.addEventListener("load", function () {
    alert('done');
    var i = JSON.parse(xhr.responseText);
    alert(i.status);
}, false);

I think you might need quotes around "upload/process" in the line:

xhr.open("post", upload/process, true);

That is sort of a guess though.