php文件上传临时存放路径为空

<input type="file" id="upfile" name="upfile" onchange="uploade()"><script type="text/javascript">
function uploade()
{
var mm = document.getElementById("upfile").files[0];
var act = new Object;
act.name = mm.name;
act.type = mm.type;
act.size = mm.size;
act.tmp_name = mm.tmp_name;
act.error = mm.error;
alert(act);
}
</script>
这是我测试的代码，alert()能弹出name,type,size的值，但是tmp_name和error的值为空