What is the difference between using PHP and JavaScript for creating a live countdown?

When creating a live countdown, the main difference between using PHP and JavaScript is that PHP is a server-side language, while JavaScript is a client-side language. This means that PHP can be used to generate the initial countdown values on the server side, while JavaScript can be used to update and display the countdown in real-time on the client side. PHP code snippet:

<?php
$target_date = strtotime("2023-01-01 00:00:00");
$current_date = time();
$diff = $target_date - $current_date;

$days = floor($diff / (60 * 60 * 24));
$hours = floor(($diff - ($days * 60 * 60 * 24)) / (60 * 60));
$minutes = floor(($diff - ($days * 60 * 60 * 24) - ($hours * 60 * 60)) / 60);
$seconds = $diff % 60;

echo "Countdown: $days days, $hours hours, $minutes minutes, $seconds seconds";
?>