Why consistency and reproducibility are important

Have you worked on a project where different Developers are developing with different tools or have different versions of packages installed?

In a development team, you want all environments to be consistent - including every Developer's local environment.

You want to have every environment to be as close as possible to each other or, ideally, identical.

You want everyone to use the same PHP version, the same web and database servers and the same packages installed.

Once things start to diverge, bugs can be introduced - such as writing code locally in a newer version of PHP than what's on production.

Ideally, you also want everything to be reproducible with locked dependencies and generate the same outcome regardless of when the commands are run.

This is one of the main reasons I've started to use Nix and devenv for projects - because they create environments that are both consistent and reproducible, reducing the chances of dependency mismatches and bugs creeping into my code.