Installing code quality tools using Composer

Most PHP: Hypertext Preprocessor (PHP) projects nowadays use Composer for a good reason. Before it entered the PHP world in 2012, keeping all external dependencies (that is, code from other developers) up to date required a lot of manual work. The required files had to be downloaded from the corresponding websites and added to the correct folders of the project. Autoloading (that is, the automatic resolving of file paths from the class name) was not standardized, if available at all. So, usually, the wanted classes needed to be actively imported using require() or require_once(). If there were any conflicts between package versions, you had to somehow solve the issues yourself.

Composer greatly simplified these efforts by solving these issues. It introduced a central repository called Packagist (https://packagist.org), where all available packages are hosted. Furthermore, it fixed the version problem by introducing version constraints...