ajax conflict?

[virap]

I have this js code to load ads from php . When I try to include it with analytics js code or create an ad unit the ipb pages go into loop.

Any idea why this js code creates a loop, loading issue?

Thank you.

 

<script type="text/javascript">
var zadajax = new XMLHttpRequest();
zadajax.onreadystatechange = function() {
if (zadajax.readyState == 4) {

document.write(zadajax.responseText);
}
};
zadajax.open("GET", "/zad.php", true);
zadajax.send(null);
</script>