What modifications are needed in the provided PHP code to ensure the visitor counter tracks unique visitors within a 24-hour period?

The issue with the current code is that it increments the visitor counter every time the page is loaded, regardless of whether the visitor is unique or not. To track unique visitors within a 24-hour period, we can use cookies to store a unique identifier for each visitor and check if that identifier has been set within the last 24 hours before incrementing the counter. 

<?php
session_start();

// Check if the unique visitor identifier cookie is set
if (!isset($_COOKIE['visitor_id'])) {
    // Generate a random unique identifier for the visitor
    $visitor_id = uniqid();
    
    // Set the visitor identifier cookie for 24 hours
    setcookie('visitor_id', $visitor_id, time() + 86400);
    
    // Increment the visitor counter
    $counter_file = 'counter.txt';
    $counter = (file_exists($counter_file)) ? file_get_contents($counter_file) : 0;
    $counter++;
    file_put_contents($counter_file, $counter);
}

// Display the visitor counter
echo 'You are visitor number: ' . $counter;
?>

Keywords

PHP visitor counter unique visitors 24-hour period tracking

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