<div id="online_status"></div>

<script type="text/javascript">
 
    function getOnlineStatus(user_id){
 
        // Make the AJAX call
        ajax("get-online-status.php", handleOnlineStatusRequest);
 
        // Javascript code continues, even while the AJAX call is being made.
        // Something could execute here ...
        // and here ...
        // ... all while we wait for a response
 
    }
 
    function handleOnlineStatusRequest(response_text){
 
        // This function is called by our 'ajax' function when the AJAX request has completed successfully.
        // 'response_text' contains any text that was sent back to us from the 'get-online-status.php' page.
 
        // Fill in the 'online_status' div with the response text from our AJAX call
        document.getElementById('online_status').innerHTML = response_text;
 
		// Set the next timeout.  We will check every 10 seconds for a change in the user's status
        setTimeout("getOnlineStatus(1)", 10000);
 
    }
 
    // Initialize the AJAX object
    function initXmlHttp(){
        // Standard Initialization
        var tmpxmlHttp;
        try {
            // Firefox, Opera 8.0+, Safari
            tmpxmlHttp = new XMLHttpRequest();
        } 
        catch (e) {
            // Internet Explorer
            try {
                tmpxmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
            } 
            catch (e) {
                try {
                    tmpxmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
                } 
                catch (e) {
                    alert("Your browser does not support AJAX!");
                    return false;
                }
            }
        }
        return tmpxmlHttp;
    }
 
    // Our AJAX function
    function ajax(url, responseHandler){
 
        // Create our AJAXy object
        var xmlHttp = initXmlHttp();
 
        // Handle changes to the object's state
        xmlHttp.onreadystatechange = function(){
 
            // Is our request complete?
            if (xmlHttp.readyState == 4) {
 
                // Request is complete (identified by a value of 4) so pass the response text into our handler function
                responseHandler(xmlHttp.responseText);
            }
        };
 
        // Open a connection
        xmlHttp.open("GET", url, true);
 
        // Make the request
        xmlHttp.send(null);
    }
 
    // Make a request for the user's status
    getOnlineStatus(1);
 
</script>

<?php
 
// Get the user ID that was handed to us
$user_id = $_GET['user_id'];
 
// We'll say the user is online
$online_status = 1;
$online_status_text = $online_status == 1 ? "Online!" : "Offline";
 
// Output the result text. Anything we output here will be sent back to the requesting page
echo ($online_status_text);
 
?>