http://stackoverflow.com/questions/36547515/php-constructor-based-dependency-inject-vs-new-which-one-is-more-efficient

Referring to my above question. What is the consequence of 'new'ing a class or inject a class in Laravel Controller?

Ex:

    public class ArticleController extends Controller
	{
		protected $articleRepo;
		protected $userRepo;
		protected $documentRepo;

		public function __construct() {
			$this->articleRepo = new ArticleRepo();
			$this->userRepo = new UserRepo();
			$this->documentRepo = new DocumentRepo();
		}
	}


	public class ArticleController extends Controller
	{
		protected $articleRepo;
		protected $userRepo;
		protected $documentRepo;

		public function __construct(ArticleRepo $articleRepo, UserRepo $userRepo, DocumentRepo $d    ocumentRepo) {
			$this->articleRepo = $articleRepo;
			$this->userRepo = $userRepo;
			$this->documentRepo = $documentRepo
		}
	}

I know Dependency injection is the best approach, but my question what is the consequence of 'new'ing them instead of injecting them? 'new'ing does it mean consumes memory?