This is a PHP library that provides a RESTful server implementation for the CodeIgniter 3 framework. It extends the base CI_Controller with automatic HTTP method routing, input parsing (GET, POST, PUT, DELETE, etc.), and output formatting (JSON, XML, CSV, HTML, etc.). The library includes built-in support for API key authentication, basic/digest auth, LDAP, rate limiting, request logging, and CORS. The core is RestController, which uses a _remap method to route requests to controller methods named like `users_get()`. The Format class handles data serialization/deserialization and is a well-crafted, standalone component. The architecture is a typical CodeIgniter library with a configuration file and optional authentication helpers. It is tightly coupled to CodeIgniter 3, meaning it is not reusable outside that framework, but it serves its purpose effectively for building REST APIs on CI3.