jQuery Ajax PHP Countdown

jQuery Ajax PHP Countdown

I'm new to Javascript and jQuery and would like some help.
 
I am running a script that counts down from 10 minutes second by second. Here is the PHP. It should be simple enough. it sets a cookie "num" that holds the total number of seconds. The rest of the script breaks it down into minutes and seconds.
  1. <?php
    $inTwoMonths = 60 * 60 * 24 * 60 + time();
    if(isset($_COOKIE['num'])){

  2.  $num = $_COOKIE['num'];
     $sec = $num`;
     if($sec<10){$sec="0$sec";}
     $min = floor($num/60);
     if($min<10){$min="0$min";}
     $num--;
     setcookie('num',$num, $inTwoMonths);





  3.  $return['msg'] = "00:$min:$sec";
     echo json_encode($return);
  4. }
    else{
     setcookie('num','600', $inTwoMonths);
    }
    ?>




I know the PHP works as I was using .load() to retrieve it.
 
I am now trying to use .ajax() as I would like the countdown to pass other variables back like a command that once it is finished to stop the jQuery script from retrieving it. I know this is by clearing the interval by using clearInterval()
 
But as I am new to javascript I do not know exactly how to pass the variables back from PHP and run an if statment and run clearInterval()
 
So far I have got this far, but it is no longer working.
  1. <script src="jquery.js"></script>
    <script>
    $(document).ready(function()
    {
    //ajaxTime.php is called every second to get time from server
    var refreshId = setInterval(function()
    {
    $.ajax({
       type: "POST",
       url: "new.php",
       success: function(msgs){
         $("#timeval").append(data.msg);
       }
     });
    }, 1000);
    //stop the clock when this button is clicked
    $("#stop").click(function()
    {
    clearInterval(refreshId);
    });
    });
    </script>
    <div id="timeval"></div>
    <button id="stop">Stop</button>























  2. Any help is greatly appriciated.