Getting ajax POST php

我正在尝试让ajax文件上传器工作，并将一些额外的表单数据传递给php。php 脚本能够获得 $_FILES['fileToUpload']，但我得到的 $_POST["fname"] 的未定义索引;

.PHP

if(isset($_FILES['fileToUpload'])){
$fname = $_POST["fname"];
$name = htmlentities($_FILES['fileToUpload']['name']);
}

JAVASCRIPT

var fd = new FormData();
fd.append("fileToUpload", document.getElementById('fileToUpload').files[0]);
var xhr = new XMLHttpRequest();
xhr.upload.addEventListener("progress", uploadProgress, false);
xhr.addEventListener("load", uploadComplete, false);
xhr.addEventListener("error", uploadFailed, false);
xhr.addEventListener("abort", uploadCanceled, false);
xhr.open("POST", "uploader.php");
xhr.send(fd);

.HTML

<form id="form1" name="form1" enctype="multipart/form-data">
                <div id="user">
                    <input type="text" id="fname" name="fname" />
                </div>
                <div id="fileInfo">
                    <div id="fileName"></div>
                    <div id="fileSize"></div>
                    <div id="fileType"></div>
                </div>
                <div class="row"></div>
                <div class="row">
                    <input type="file" name="fileToUpload" id="fileToUpload" onchange="fileSelected();"/>
                </div>
                <div class="row">
                    <input type="button" onclick="uploadFile()" value="Upload" />