Chances are your code already uses one of the HTTP PSRs in some way. In this 'no slides, just code' session we'll take a hands on look at how HTTP Messages (PSR-7) and HTTP Handlers (PSR-15) work, and how they can be properly leveraged. HTTP messages provide a considerable advantage over global variables, and their immutability actually makes it easier to confidently modify an incoming request or an outgoing response in your web application. HTTP handlers are a common concept in micro-frameworks, and PSR-15 provides a way to create reusable framework-agnostic code. But that's not all it provides. The HTTP handler interface can be used to inject the concept of middleware into an existing application without having to introduce a new framework. Or to easily build a lightweight application without any framework. Take a guided tour through both PSRs, and find out how you can used them effectively in your current codebase. What you'll learn from this talk: - the value in immutable HTTP Request objects - how to evolve an HTTP Request object - how to extend a library's HTTP Request object - how a middleware stack works - how easy it is to use PSR-7 & PSR-15 without any framework This talk was given at the Dutch PHP Conference in 2021, organised and hosted by Ibuildings. Visit https://phpconference.nl or https://ibuildings.nl for more information.