Traits

Traits inject methods/properties into classes without establishing an is-a relationship. They are useful for focused implementation fragments but can hide dependencies when overused.

Practical example

<?php
trait Timestamps { public function touch(): void { $this->updatedAt = new DateTimeImmutable(); } }
final class Article { use Timestamps; private DateTimeImmutable $updatedAt; }

Resolve collisions with insteadof and alias/change visibility with as. Trait methods can depend on abstract requirements. Prefer collaborators when behavior has state, configuration, or an independently testable lifecycle.