请问各位大虾，我这段上传代码有什么问题吗？为什么老是提示上传失败啊？
<?        
                  $dir=getcwd();
        echo $dir;
        $uploadfile=$dir."\\".$_FILES['userfile']['name'];
        print "<pre>";
        if(move_uploaded_file($_FILES['userfile']['tmp_name'],$uploadfile))
        {
            print "上传成功，以下是调试信息：\n";
            print_r($_FILES);
        }
        else
        {
            print "上传失败，以下是调试信息：\n";
            print_r($_FILES);
        }
        print "</pre>";
    
?>