Joomla ajax上传没有收到文件

Question

我正在使用像这样的ajax上传文件：

var data = new FormData();
    jQuery.each(files, function(key, value)
    {
        data.append(key, value);
    });
    jQuery.ajax({
        url: "<?php echo JURI::base().'modules/xxx/ajax_upload.php' ?>",
        type: 'POST',
        data: data,
        cache: false,
        dataType: 'json',
        processData: false, // Don't process the files
        contentType: false, // Set content type to false as jQuery will tell the server its a query string request
        success: function(data)
        {
            if(typeof data.error === 'undefined')
        {
            // Success so call function to process the form
            //submitForm(event, data);
        }
        else
        {
            // Handle errors here
            console.log('ERRORS: ' + data.error);
        }
        },
        error: function(jqXHR, textStatus, errorThrown)
        {
            // Handle errors here
            console.log('ERRORS: ' + textStatus);
            // STOP LOADING SPINNER
        }
    });

在控制台中我看到图像已发送，但在ajax_upload.php中我无法获取文件，尝试使用：

print_r($_FILES);
print_r($_POST);

并返回空数组，表单有enctype="multipart/form-data"