파일 전송 버튼없이 전송하기

<?
echo "Filename : ".$_FILES['fff']['name']."<br>";
echo "Tmp_name : ".$_FILES['fff']['tmp_name']."<br>";
?>
<html>
<body>
<form name=aaa action="test4.php" method="post" enctype="multipart/form-data">
<input type=file name=fff onchange=aa();>
</form>

</body>
</html>

<script>
function aa(){
if(document.aaa.fff.value != ""){
document.aaa.action = "test4.php";
document.aaa.submit();
}
}
</script>