PHP开发指南：如何实现网站访问权限控制

CREATE TABLE `users` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(255) NOT NULL,
  `password` varchar(255) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `username` (`username`)
);

CREATE TABLE `permissions` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `user_id` int(11) NOT NULL,
  `page` varchar(255) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `user_id` (`user_id`)
);

<!-- login.html -->
<h2>用户登录</h2>
<form action="login.php" method="POST">
  <label for="username">用户名：</label>
  <input type="text" id="username" name="username" required><br>
  <label for="password">密码：</label>
  <input type="password" id="password" name="password" required><br>
  <input type="submit" value="登录">
</form>

// login.php
<?php
session_start();
$servername = "localhost";
$username = "root";
$password = "123456";
$dbname = "your_database_name";

// 创建数据库连接
$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接是否成功
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 从登录表单获取用户名和密码
$username = $_POST['username'];
$password = $_POST['password'];

// 在用户表中验证用户信息
$sql = "SELECT * FROM users WHERE username='$username' AND password='$password'";
$result = $conn->query($sql);

// 如果存在匹配的用户记录，则认为登录成功，把用户信息存入session
if ($result->num_rows > 0) {
    $row = $result->fetch_assoc();
    $_SESSION['user_id'] = $row['id'];
    $_SESSION['username'] = $row['username'];
    header("Location: index.php"); // 重定向到首页
} else {
    echo "用户名或密码错误";
}

$conn->close();
?>

// index.php
<?php
session_start();
// 检查用户是否登录
if (!isset($_SESSION['user_id'])) {
    header("Location: login.html"); // 重定向到登录页面
    exit();
}

// 创建数据库连接
$servername = "localhost";
$username = "root";
$password = "123456";
$dbname = "your_database_name";
$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接是否成功
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 获取当前页面的URL
$page = $_SERVER['PHP_SELF'];

// 检查当前用户是否具有访问当前页面的权限
$user_id = $_SESSION['user_id'];
$sql = "SELECT * FROM permissions WHERE user_id='$user_id' AND page='$page'";
$result = $conn->query($sql);

// 如果没有匹配的访问权限，则重定向到没有权限的页面
if ($result->num_rows == 0) {
    header("Location: no_permission.html");
    exit();
}

$conn->close();
?>