在PHP中实现权限

CREATE TABLE `permissions` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) NOT NULL,
  `description` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `roles` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) NOT NULL,
  `description` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `role_permissions` (
  `role_id` int(11) NOT NULL,
  `permission_id` int(11) NOT NULL,
  PRIMARY KEY (`role_id`,`permission_id`),
  FOREIGN KEY (`role_id`) REFERENCES `roles` (`id`) ON DELETE CASCADE,
  FOREIGN KEY (`permission_id`) REFERENCES `permissions` (`id`) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `users` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(50) NOT NULL,
  `password` varchar(255) NOT NULL,
  `role_id` int(11) NOT NULL,
  PRIMARY KEY (`id`),
  FOREIGN KEY (`role_id`) REFERENCES `roles` (`id`) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

function check_permission($user_id, $permission_name) {
  // 查询用户所在的角色
  $role_id = query("SELECT role_id FROM users WHERE id = ?", [$user_id])[0]['role_id'];

  // 查询角色所拥有的权限
  $permissions = query("SELECT permissions.name FROM role_permissions INNER JOIN permissions ON role_permissions.permission_id = permissions.id WHERE role_permissions.role_id = ?", [$role_id]);

  // 检查权限是否存在于角色所拥有的权限中
  foreach ($permissions as $permission) {
    if ($permission['name'] == $permission_name) {
      return true;
    }
  }

  return false;
}