Can't solve Javascript Timer - countdowntimer

Question

My timer on this page http://jian.comoj.com/countdown.php isn't counting down. I follow a video tutorial on doing this but somehow something is wrong and I don't know what it is.
<?php
include "connect.php";
$query= "select * from product where product_id='1'";
$result= mysql_query($query);
$record= mysql_fetch_object($result);
$time= $record->end_time;
date_default_timezone_set('Asia/Singapore');
$unix_time= strtotime($time);
?>
<script type="text/javascript">
function countdown(){
<?php
$now= time();
$sec= $unix_time-$now;
$min= $sec/60;
$hour= $min/60;
$sec %= 60;
$min %= 60;
?>
var hour= <?php echo floor($hour); ?>;
var min= <?php echo $min; ?>;
var sec= <?php echo $sec; ?>;
document.getElementById("hour").innerHTML = hour;
document.getElementById("min").innerHTML = min;
document.getElementById("sec").innerHTML = sec;
setInterval('countdown()',1000);
}
</script>
<div id="hour"></div>
<div id="min"></div>
<div id="sec"></div>
<script type="text/javascript">countdown();</script>

Answer 1

function countdown(){
var hour= 3;
var min= 39;
var sec= 58;
document.getElementById("hour").innerHTML = hour;
document.getElementById("min").innerHTML = min;
document.getElementById("sec").innerHTML = sec;
setTimeout('countdown()',1000);
}
LOOK AT THE FUNCTION THEY ARE FIXED i.e hour, min and sec.