In PHP 8.1, Fibers are a new feature that allows lightweight and controlled concurrency. But what is Fiber really? A Fiber is a code block that maintains its own stack of variables and state and can be started, suspended, and terminated cooperatively with the main code. You can understand Fibers as threads in computer program. We will look at how Fibers work, how they are constructed, and how they might be applied in some examples during the session.