如何使用PHP在dropzone.js中提交后计算文件？

I'm using dropzone.js to upload files and then count the files after submit using php, but why the result is 1 ??

My dropzone js:

Dropzone.autoDiscover = false;

var myDropzone = new Dropzone("#drop", {
 url: 'test.php',

 previewsContainer: "#previews",
 clickable: "#clickable",
 autoQueue: false,
 addRemoveLinks: true
});

document.querySelector("#butt").onclick = function() {
  myDropzone.enqueueFiles(myDropzone.getFilesWithStatus(Dropzone.ADDED));
};

myDropzone.on("complete", function(file) {
  myDropzone.removeFile(file);
});
myDropzone.on('sending', function (file, xhr, formData) {
 formData.append("Username", document.getElementById("Username").value);
 formData.append("token", document.getElementById("token").value);
});

My test.php :

$ds = DIRECTORY_SEPARATOR; 

$storeFolder = 'uploads'; 
if(!empty($_FILES)) {
  $count = count($_FILES['file']['name']);
  $tempFile = $_FILES['file']['tmp_name'];        
  $targetPath = dirname( __FILE__ ) . $ds. $storeFolder . $ds; 

  $targetFile =  $targetPath. $count."-".$_FILES['file']['name'];

  move_uploaded_file($tempFile,$targetFile);
}else{
  return "fail";
}

Or maybe there is another method to count the files ?