问如何用PHP实现权限管理功能

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

CREATE TABLE `roles` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
);

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

CREATE TABLE `role_permissions` (
  `role_id` int(11) NOT NULL,
  `permission_id` int(11) NOT NULL,
  PRIMARY KEY (`role_id`, `permission_id`)
);

class User {
  public $id;
  public $username;
  public $password;
  public $role;
}

class Role {
  public $id;
  public $name;
  public $permissions = [];
}

class Permission {
  public $id;
  public $name;
}

function userHasPermission(User $user, Permission $permission) {
  foreach ($user->role->permissions as $userPermission) {
    if ($userPermission->id === $permission->id) {
      return true;
    }
  }
  return false;
}

// 获取用户
$user = getUserFromDatabase($userId);

// 获取要检查的权限
$permission = getPermissionFromDatabase("edit_posts");

// 检查用户是否具有权限
if (userHasPermission($user, $permission)) {
  // 允许用户编辑文章
} else {
  // 拒绝访问
}