Tool
Composer
The PHP package manager: autoload, lockfile, semver — the difference between a project and a zip of files.
Composer’s particularity is composer.lock: the same versions on every machine, including CI. PSR-4 autoload replaced require_once jungles. platform php in composer.json is a contract with production.
A senior treats update as a review, not a habit. Private Packagist or a GitLab package registry keeps internal libraries out of copy-paste.
Without Composer there is no modern PHP ecosystem. With it, the skill is dependency hygiene, not “installing packages”.
