问无法使用php和纯ajax上载大型文件

EN

 upload_max_filesize = 9000M

function _(el){
   return document.getElementById(el);
}
function uploadFile(){
   var file = _("file1").files[0];
   var formdata = new FormData();
   formdata.append("file1", file);
   var ajax = new XMLHttpRequest();
   ajax.addEventListener("load", completeHandler, false);
   ajax.addEventListener("error", errorHandler, false);
   ajax.addEventListener("abort", abortHandler, false)
   ajax.open("POST", "index.php");
   ajax.send(formdata);
 }
 function completeHandler(event){
     _("status").innerHTML = event.target.responseText;
     _("progressBar").value = 0;
}
function errorHandler(event){
    _("status").innerHTML = "Upload Failed";
}
function abortHandler(event){
   _("status").innerHTML = "Upload Aborted";
} 

<?php
  $fileName = $_FILES["file1"]["name"]; e
  $fileTmpLoc = $_FILES["file1"]["tmp_name"]; 
  $fileType = $_FILES["file1"]["type"]; 
  $fileSize = $_FILES["file1"]["size"]; 
  $fileErrorMsg = $_FILES["file1"]["error"]; 
  if (!$fileTmpLoc) { 
    echo "ERROR: Please browse for a file before clicking the upload button.";
   exit();
 }
 if(move_uploaded_file($fileTmpLoc, "uploads/$fileName")){
    echo "$fileName upload is complete";
 } else {
    echo "move_uploaded_file function failed";
 }
?>

 Notice: Undefined index: file1 in C:\wamp\www\test\index.php on line 2
 Notice: Undefined index: file1 in C:\wamp\www\test\index.php on line 3
 Notice: Undefined index: file1 in C:\wamp\www\test\index.php on line 4
 Notice: Undefined index: file1 in C:\wamp\www\test\index.php on line 5
 Notice: Undefined index: file1 in C:\wamp\www\test\index.php on line 6

ERROR: Please browse for a file before clicking the upload button.
Uploaded 34209942 bytes of 34209942