The PHP Script

There is many techniques to track online visitors with PHP, in this example I used the most simple one. The script check the sessions online and then consider the recent ones in an interval of about 3 minutes. This gives more realistic information, because visitors idle for a long period are considered not online, and in the same time we don't have to create complex script and store informations in database ... etc.

// idle time in minutes
define("MAX_IDLE_TIME", 3); 

function who(){

	$path = session_save_path();

	if (trim($path)=="") {

		return FALSE;

	}

	$d = dir( $path); $i = 0;

	while (false !== ($entry = $d->read())) {

			

		if ($entry!="." and $entry!="..") {

			if (time()- filemtime($path."/$entry") < MAX_IDLE_TIME * 60 ) {

				$i++;

			}

		}

	}

	$d->close();

	

	return $i;

}

AJAX code

The javascript didn't change a lot, we just have less code. What we need in this case is just getting the data and display it, nothing to parse or to change. Timer have been set to update the counter every minute.

var RequestObject = false; // XMLHttpRequest Object
var Backend = 'http://www.phpmagazine.net/demo/ajaxonline/check.php'; // Counter url
window.setInterval("update_timer()", 60000); // update the data every 1 min

The main AJAXRequest and the ReqChange function in our case will be

/*
* Main AJAX online Visitor counter request
*/
function AJAXRequest() {

	// change the message to Checking online ...

	document.getElementById("online").innerHTML = "Checking online ...";

	

	// Prepare the request

	RequestObject.open("GET", Backend , true);

	// Set the onreadystatechange function

	RequestObject.onreadystatechange = ReqChange;

	// Send

	RequestObject.send(null); 

}

/*

* onreadystatechange function

*/

function ReqChange() {

	// If data received correctly

	if (RequestObject.readyState==4) {

	

		// if data is valid

		if (RequestObject.responseText.indexOf('invalid') == -1) 

		{ 	

			// getting the response

			 var msgs = RequestObject.responseText.split('|');

		

			// Tell the reader the everything is done

			document.getElementById("online").innerHTML = msgs[0]+" visitors online";

			

		}

		else {

			// Tell the reader that there was error requesting data

			document.getElementById("online").innerHTML = "Error Requesting data";

		}

	}

	

}

In addition to this script I have used a div "online" that you can put anywhere in your page

AJAX online visitors

This is another way to use AJAX with PHP to retrieve information about online visitors, you can test the AJAX Online visitor script online, the PHP Script you can get it from here.