How to implement Heatmap on Websites using PHP, MySQL, jQuery and Ajax?

I was assigned a task when an Interviewer interviewed me and that was a Technical question. I was asked to design a system that can gather click data from a webpage and show it later in form of a Heatmap.

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This system can be integrated into any website which records visitor clicks on the page. The goal of of this will be to track visitor’s mouse clicks on various elements of the page and later show them accurately in form a Heatmap. The owner should be able to see aggregated click data in form of an overlay on top of his webpage. The areas in the heatmap that are red more clicks compared to the areas that are white.

After googling through the internet I found some resources which were very interesting. I devoted some time and tried to implement a demo. Please follow the following Steps:

1. Client Code : Create a file index.php and include the following code below. This is the page where users make clicks.

[code]
<script type=’text/javascript’ src="js/jquery-lib.js"></script> <!– jQuery library –>
<script type=’text/javascript’ src="js/hm-dev.js"></script> <!– Log JS –>

<title>99-Websites.com Labs</title>
<body>
<div style="text-align:center">
<img src="99-ws-labs.jpg" />
</div>
</body>

[/code]

2. The Ajax Call : Create a JS file named as hm-dev.js. This file is included in the above index.php page. Add the snippet below:

[code]
/*
Author : Dev
Date : 12/06/2015
*/

jQuery(document).ready(function() {
jQuery(document).click(function(e){
//alert(window.location.href.toString().split(window.location.host)[1]+" — "+e.pageX+" — "+e.pageY);
log_click(window.location.href.toString(), e.pageX, e.pageY);
});
var canvas = document.getElementsByTagName(‘canvas’)[0];
canvas.style.display = "none";
});

function log_click(page, x, y){ // log clicks for heatmap
jQuery.ajax({
type: ‘POST’,
url: ‘log_click.php’,
crossDomain: true,
data: "x_coord="+x+"&y_coord="+y+"&page="+page,
dataType: ‘json’,
success: function(responseData, textStatus, jqXHR)
{
if (responseData== 1){
console.log("Click logged: " + x + ", " + y);

}
else{
console.log("Error – click not logged " + x + ", " + y);
}
},
error: function (responseData, textStatus, errorThrown)
{
console.warn(responseData, textStatus, errorThrown);
alert(‘CORS failed – ‘ + textStatus);
}
});
}
[/code]

3. Log the Clicks : Create a PHP file named with log_click.php and add the following snippet.

[code]

<?php
header(‘Access-Control-Allow-Origin: *’);
header(‘Access-Control-Allow-Methods: POST, GET, OPTIONS’);
header(‘Access-Control-Max-Age: 1000’);
header(‘Access-Control-Allow-Headers: Content-Type’);

//echo json_encode(array("your_request_was" => $_POST[‘page’].$_POST[‘x_coord’].$_POST[‘y_coord’]));

include(‘config.php’); //Create config.php file and define $dbuser, $dbpass & $dbname

if(isset($_POST[‘x_coord’])){
$page = htmlentities($_POST[‘page’]);
if($page == "/"){ $page = "/index.php"; }
$xcoord = htmlentities($_POST[‘x_coord’]);
$ycoord = htmlentities($_POST[‘y_coord’]);
$time = date( ‘Y-m-d H:i:s’);

$conn = mysql_connect(‘localhost’, $dbuser, $dbpass);
mysql_select_db($dbname, $conn);
$page = mysql_real_escape_string($page);
$xcoord = mysql_real_escape_string($xcoord);
$ycoord = mysql_real_escape_string($ycoord);

mysql_query("INSERT INTO clicks (timestamp, page, x, y) VALUES (‘$time’, ‘$page’, $xcoord, $ycoord)");
mysql_close($conn);
echo "1";
}
else
{
echo ‘0’;
}

?>

[/code]

4. Create MySQL Table : Create table with following fields:

[code]

CREATE TABLE IF NOT EXISTS `clicks` (
`timestamp` datetime NOT NULL,
`page` varchar(200) NOT NULL,
`x` int(255) NOT NULL,
`y` int(255) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

[/code]

That’s it, the first part is over. After implementing the above steps you will be able to log clicks on the MySQL Table. The next and the main part is viewing the heat maps.

5. Create the Admin Page : Create PHP page named with admin.php. This page will lists out all the domains on which the client side code is added. When the links are clicked, their respective heatmaps will be displayed below the same page.  Admin Code is listed below:

[code]

<?php
/*
Author : Dev
Date : 12/06/2015
*/
include("config.php");
$con2 = mysql_connect(‘localhost’, $dbuser, $dbpass);
mysql_select_db($dbname, $con2);
$query = "SELECT distinct page FROM `clicks` WHERE 1";
$result = mysql_query($query);
?>
<html>
<head>
<title>Heatmap Admin</title>
<script type=’text/javascript’ src="js/jquery-lib.js"></script>

<script type=’text/javascript’ src="js/heatmap.js"></script>
<script>
jQuery(document).ready(function(){
var heatmapInstance = h337.create({
container: document.querySelector(‘.display’),
radius: 25
});

jQuery(".showcanvas").click(function(){
//location.reload();
//alert(jQuery(this).attr(‘value’));
var timescale = "day";
var page = jQuery(this).attr(‘value’);
//alert(page);
var postData = "timescale="+timescale+"&page="+page;
jQuery.ajax({
type:"POST",
dataType: "json",
data: postData,
beforeSend: function(x) {
if(x && x.overrideMimeType) {
x.overrideMimeType("application/json;charset=UTF-8");
}
}, url: ‘heatmap.php’,
success: function(data) {

if (data.amount > 0){
for (i=0; i<data.amount; i++){
heatmapInstance.addData({
x: data[i].x,
y: data[i].y,
value: 2
});
}
}
}
});

});
});
</script>
</head>
<body >
<div style="width:100%; border:1px solid; black;">
[Click on the Websites below to View their respective HeatMaps]<br>
<ul style="font-size:12px;">
<?php
while($row = mysql_fetch_assoc($result)){
?>
<li><a href="#" class="showcanvas" value="<?=$row["page"]?>"> <?=$row["page"]?></a></li> <br/>

<?php

}
?>
</ul>
</div>
<div class="display" style="width:100%;height:100%;border:1px solid; black;float:right;">
</div>

</body>
</html>

[/code]

The main logic behind the code is the heatmap.js library. In order to understand in detail you can explore the following references:

1. http://www.patrick-wied.at/static/heatmapjs/example-click-heatmap.html

2. http://rossmarks.co.uk/blog/?p=683

3. http://www.d-mueller.de/blog/cross-domain-ajax-guide/

You can view the Demo here: 

1. Client / Users Page : http://99labs.net where you can make some clicks on the webpage.

2. Admin Page : http://dewendra.com.np/labs/hm/admin.php where you can view the Heatmap.

Also, You can download the whole code from here : Download

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PS : The client code can be installed into any website and their logs can be maintained on the remote server. If you go through the client side code you can see the ajax code implemented with CORS (Cross Origing Resource Sharing) using jQuery.

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