Composer has definitely made a huge impact on how PHP packages and libraries are integrated into other applications. Sometimes, though, it makes more sense for you to keep your code internal to the organization rather than have it public where Composer can install it. In this case, using some thing like Satis (a self-hosted Packagist-ish server) makes more sense.

We all love Composer. It changed dramatically the way we build PHP applications, based on small and reusable components, but this creates new challenges, especially when we have a single point of failure (SPO). With Satis, the deployment process can be made robust by adding redundancy in all potential SPOFs (Packagist and GitHub). Let’s see how it works.

They start with a brief look at how Composer works for those not familiar, making the connection with Packagist and ultimately the public repository. In the context of the "single point of failure" they talk about Packagist being down and it preventing the install (or deployment!) of your application. Satis is prefect to help prevent this. The article then shows how to install Satis (via Composer, naturally) and how to set up the configuration file to define the repositories. The server is then built and can be run using the built-in PHP server on the port of your choice. They include a screenshot of the end result and a quick example of how to use it via your project's Composer configuration.