php中的简单授权/登录功能

<form action="login.php" method="post">
 <label for="username">用户名:</label>
 <input type="text" id="username" name="username" required>

 <label for="password">密码:</label>
 <input type="password" id="password" name="password" required>

 <input type="submit" value="登录">
</form>

<?php
session_start();

// 假设已经从数据库中获取到了用户信息
$users = [
    ['username' => 'admin', 'password' => 'password123'],
    ['username' => 'user', 'password' => 'password456']
];

$username = $_POST['username'];
$password = $_POST['password'];

foreach ($users as $user) {
    if ($user['username'] === $username && $user['password'] === $password) {
        $_SESSION['username'] = $username;
        header('Location: protected_page.php');
        exit;
    }
}

// 如果用户名或密码错误，则显示错误消息
echo '用户名或密码错误，请重试。';

<?php
session_start();

if (!isset($_SESSION['username'])) {
    header('Location: login.php');
    exit;
}

echo '欢迎，' . $_SESSION['username'] . '！';