Running a file via Ajax?

[Hendrick]

Hi.

 

I am newer to Ajax.  I have known PHP for about a year now.  So basically, I am trying to have ajax run a file every half second.  The file is a simple connect to the database, and update the database.

 

I followed this tutorial:

http://www.ajaxfreaks.com/tutorials/2/0.php

 

Heres my script.  Any help?

<script type="text/javascript">
    function createRequestObject() {
    
        var req;
    
        if(window.XMLHttpRequest){
            // Firefox, Safari, Opera...
            req = new XMLHttpRequest();
        } else if(window.ActiveXObject) {
            // Internet Explorer 5+
            req = new ActiveXObject("Microsoft.XMLHTTP");
        } else {
            // There is an error creating the object,
            // just as an old browser is being used.
            alert('There was a problem creating the XMLHttpRequest object');
        }
    
        return req;
    
    }
    
    // Make the XMLHttpRequest object
    var http = createRequestObject();
    
    function sendRequest(act) {
        
        // Open PHP script for requests
        http.open('get', 'query.php?u=<?php echo $u; ?>&b=<?php echo $b; ?>');
        http.onreadystatechange = handleResponse;
        http.send(null);
    
    }
    
    function handleResponse() {
    
        if(http.readyState == 4 && http.status == 200){
    
            if(response) {
                // UPDATE ajaxTest content
                document.getElementById("countPosts").innerHTML = response;
                setTimeout(countPosts,5000);
            }
    
        }
    }

    function countPosts() {
        sendRequest('countPosts');
    }
</script>

 

The query.php file does work fine.  I already tested that out, hoping it was the issue.