How can AJAX and timer functions be used in PHP to achieve real-time data updates on a webpage?

To achieve real-time data updates on a webpage using AJAX and timer functions in PHP, you can create a PHP script that fetches updated data from a database or an external API at regular intervals. This script can be called asynchronously using AJAX to update specific parts of the webpage without refreshing the entire page. Additionally, you can use JavaScript timer functions like setInterval to periodically trigger the AJAX request for continuous updates.

<?php
// PHP script to fetch updated data from a database or API
// This script can be called asynchronously using AJAX

// Code to fetch updated data
// For example, fetching data from a database
$data = fetchDataFromDatabase();

// Output the data as JSON
echo json_encode($data);
?>