Wrong if statement jquery - php

Question

So I have a counter which counts down to 0 so when it hits 0 I want it to do a pdo update. The problem is that the if statement lets the update happen on each page refresh and does not wait for the count to hit 0.
I have looked at the code and can not see where I am going wrong.
<?php $timer = '20'; ?>
window.onload = function(){
(function(){
var counter = <?php echo $timer ; ?>;
setInterval(function() {
counter--;
if (counter >= 0) {
span = document.getElementById("count");
span.innerHTML = counter;
}
// Display 'counter' wherever you want to display it.
if (counter === 0) {
document.getElementById( "response" ).innerHTML = "<div style=\"float: right; display: inline-block; margin: 6px;\"><div class=\"skip_btn\">
<?php
$sqll = "UPDATE users SET coins=coins+? WHERE username=?";
$q = $db->prepare($sqll);
$q->execute(array('1',$_SESSION['username']));
$sqll2 = "UPDATE websites SET clicks_left=clicks_left-? WHERE id=?";
$q2 = $db->prepare($sqll2);
$q2->execute(array('1',$row['id']));
?>
</div></div><div style=\"clear:both;\"></div>";
}
}, 1000);
})();
}
I have just fixed it buy using a parser
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript">
// Check if the page has loaded completely
$(document).ready( function() {
setTimeout( function() {
$('#some_id').load('parser.php');
}, 10000);
});
</script>
Thanks for the warm welcome tot he site tho.

Answer 1

Using jQuery try the following:
$(document).ready(function() {
var counter = 20;
setInterval(function() {
if( counter == 0 ) {
$.post("url/to/php");
}
else {
$("#div_for_showing_counter").html(counter);
counter--;
}
}, 1000);
});
This way you separate client side from server side. You can do whatever you want in the php file. If you need a callback or you need to pass data to the php file then simply modify the $.post to something like this:
$.post("url/to/php", { "key1": "value1", "key2": "value2" }, function(data) {
alert(data);
});