Try to make ajax php back button work - php

Question

I try to make the php and ajax back button work by using pushState() and popstate(). I got the pushState somehow working, but the popState is not.
for ($i=1; $i<=$lastPage; $i++) {
//$pageLink[] = ''.$i.'';
$pageLink[] = ''.$i.'';
};
java script below.
<script>
function showmerchantitems(str, str2) {
var elements = document.getElementsByClassName("itemwrapper");
if (str.length == 0) {
for (var i = 0; i < elements.length; i++) {
elements[i].innerHTML = "";
}
return;
} else {
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
for (var i = 0; i < elements.length; i++) {
elements[i].innerHTML = this.responseText;
}
}
};
xmlhttp.open("GET", "ajax.php?action=merchantlistpage&merchant_id=" + str + "&p=" + str2, true);
xmlhttp.send();
history.pushState(null, "", "ajax.php?action=merchantlistpage&merchant_id=" + str + "&p=" + str2);
$(window).bind("popstate", function(){
$.getScript(location.href);
});
}
}
</script>