Can you explain the concept of "Challenge-ID" in PHP form submissions and how it can help prevent duplicate data submissions?

The concept of "Challenge-ID" in PHP form submissions involves generating a unique identifier for each form submission and storing it in a session variable. This identifier is then checked upon form submission to prevent duplicate data submissions. By implementing this, it helps prevent users from accidentally submitting the same data multiple times.

<?php
session_start();

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    if (!isset($_SESSION['challenge_id'])) {
        $_SESSION['challenge_id'] = uniqid();
    }

    if ($_POST['challenge_id'] == $_SESSION['challenge_id']) {
        // Process form submission
        // Prevent duplicate data submissions
        unset($_SESSION['challenge_id']);
    } else {
        // Display error message for duplicate submission
    }
}
?>