PHP开发技巧：如何实现用户权限控制

CREATE TABLE users (
  id INT(11) AUTO_INCREMENT PRIMARY KEY,
  username VARCHAR(50) NOT NULL,
  password VARCHAR(255) NOT NULL,
  role_id INT(11) NOT NULL
);

CREATE TABLE roles (
  id INT(11) AUTO_INCREMENT PRIMARY KEY,
  name VARCHAR(50) NOT NULL
);

CREATE TABLE permissions (
  id INT(11) AUTO_INCREMENT PRIMARY KEY,
  name VARCHAR(50) NOT NULL,
  resource VARCHAR(50) NOT NULL
);

CREATE TABLE role_permissions (
  id INT(11) AUTO_INCREMENT PRIMARY KEY,
  role_id INT(11) NOT NULL,
  permission_id INT(11) NOT NULL
);

session_start();

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
  $username = $_POST['username'];
  $password = $_POST['password'];

  // 连接数据库并查询用户信息
  $conn = new mysqli('localhost', 'username', 'password', 'database');
  $query = "SELECT * FROM users WHERE username='$username' AND password='$password'";
  $result = $conn->query($query);

  if ($result->num_rows == 1) {
    $row = $result->fetch_assoc();
    $_SESSION['user_id'] = $row['id'];
    $_SESSION['username'] = $row['username'];
    $_SESSION['role_id'] = $row['role_id'];
    header('Location: dashboard.php');
    exit;
  } else {
    $error = "Invalid username or password";
  }
}

// 如果用户已登录，则跳转至仪表盘（dashboard）页面
if (isset($_SESSION['user_id'])) {
  header('Location: dashboard.php');
  exit;
}

function checkPermission($resource) {
  // 检查用户是否已登录
  if (!isset($_SESSION['user_id'])) {
    header('Location: login.php');
    exit;
  }
  
  // 查询用户角色的权限
  $conn = new mysqli('localhost', 'username', 'password', 'database');
  $query = "SELECT permissions.name FROM (roles INNER JOIN role_permissions ON roles.id = role_permissions.role_id) INNER JOIN permissions ON role_permissions.permission_id = permissions.id WHERE roles.id = {$_SESSION['role_id']} AND permissions.resource = '$resource'";
  $result = $conn->query($query);
  
  if ($result->num_rows == 0) {
    header('Location: unauthorized.php');
    exit;
  }
}

// 调用权限验证函数来限制访问
checkPermission('dashboard.php');