Calling a PHP page and showing its output every second with AJAX. For ease of use, this requires Jquery.

This example will show the current datetime as per the PHP timezone setting.

index.html:

<script src="https://write.corbpie.com/wp-content/litespeed/localres/aHR0cHM6Ly9jZG5qcy5jbG91ZGZsYXJlLmNvbS8=ajax/libs/jquery/3.4.1/jquery.min.js"></script>
<script type="text/javascript">
    setInterval(function () {
        $.ajax({
            url: 'datetime.php',
            success: function (data) {
                $('.datetime').html(data);
            }
        });
    }, 1000);
</script>
<div class="datetime"></div>

datetime.php:

<?php
echo date('Y-m-d H:i:s');

All datetime.php does is echo the date as per the format, the AJAX setinterval function will call datetime.php every 1 second and put its output into the HTML div with class=datetime

This example serves no real purpose an actual use would be fetching value/s from a database and displaying them in real-time considering the fetching and updating the div every 1 second.