Dependency Injection

Dependency Injection — a practical guide to dependency injection PHP with clear examples you can reuse in real projects.

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Short description

Dependency Injection (DI) improves testing and flexibility. Inject interfaces, not concrete classes, when useful.

Constructor injection

interface Mailer { public function send(string $to, string $body): void; }
class WelcomeService {
    public function __construct(private Mailer $mailer) {}
    public function welcome(string $email): void {
        $this->mailer->send($email, 'Welcome!');
    }
}