session-based-rate-limiter.php

<h1>Super Awesome Session-Based Rate Limiter</h1>

<?php

session_start();

$blocked = false;
$message = "You may pass.";
$now = new \DateTime();
$attempts = isset($_SESSION['attempts']) ? $_SESSION['attempts'] : [];

if (count($attempts) > 4) {
    $oldest = new \DateTime($attempts[0]);
    
    if ($oldest->modify('+1 minute') > $now) {
        $blocked = true;
    }
}

array_unshift($attempts, $now->format(\DateTime::ISO8601));
$attempts = array_slice($attempts, 0, 5);
$_SESSION['attempts'] = $attempts;

if ($blocked) {
    $message = "YOU SHALL NOT PASS!";
}

?>

<p><strong><?= $message ?></strong></p>

<p>ATTEMPTS: <?= count($attempts); ?></p>
<ul>
    <?php foreach ($attempts as $attempt): ?>
        <li><?= $attempt; ?></li>
    <?php endforeach; ?>
</ul>