Gateway and repository pattern PHP Laravel

Question

I wanna ask about design pattern.

Why should I use dependency injection in constructor, not import it ('use statement')?

For example:

in my controller:

class AuthController extends Controller {

    public function __construct(UserGateway $userGateway)
    {
        $this->userGateway = $userGateway;
    }

    public function doSomething()
    {
        $this->userGateway->foo();
    }

}

Why don't use just like this instead?

use Acme\UserGateway;
class AuthController extends Controller {

    public function doSomething()
    {
        UserGateway::foo();
    }

}

Many thanks.

Answer 1

Assuming UserGateway is not laravel facade: here's the biggest advantage of injecting stuff this way: in the future, you might redefine what UserGateway actually is, and supply some other class (most often, it's subclass) instead of it like this:

$this->app->bind(UserGateway::class, function ($app) {
    return new NewUserGateway();
});

This is extremely useful for overriding some parts of your code, especially if you're using same packages across multiple projects. And it does not require you to change the AuthController's code.

If UserGateway is a Facade, the only benefit you'll get is a better code navigation with you IDE, since it will know what class exactly are you referencing (assuming that you didn't re-bound it).