This document discusses building REST APIs. It begins with introductions and then provides an overview of REST including: - REST is based on HTTP and uses common methods like GET, POST, PUT, DELETE. - Resources are represented as URIs and can be acted on via HTTP methods rather than function calls. - Responses use standard HTTP response codes to indicate success or errors. - Authentication is typically done with tokens rather than cookies to maintain statelessness. - The Symfony framework is well-suited for building REST APIs in PHP due to its maturity and object-oriented architecture.