Is it dependency injection and is it a bad practice?

Question

I have a small framework and I coded it like this. I\'m not sure if it is called dependency injection or not. I don\'t know if it is like a design pattern or not. I also don\'t

Answer 1

1. Your FrameWork_Engine_Model is a registry (Registry Pattern). Injecting the registry as dependency into all objects is kind of a misunderstood dependency injection. Technically it is DI, but you create a dependency from everything to everything and also take away the flexibility that DI should offer.
2. If your FrameWork_Engine_Model was meant to instantiate services and manage their dependencies, you could change it to an Inversion of Control Container (typical pattern related to DI)
3. No, not in general.

I won't argue your choice of class names and the responsibilities of your services and controllers, as I don't think it is within scope of this question. Just a remark: it looks like your controllers do too much. If you are interested in clean code, you might want to have a look at the Single Responsibility Principle and keep your controllers "thin", moving business logic and database queries to a service layer and output mechanisms like bbcode to views.

So, back to your example and how to change it to a sensible usage of Dependency Injection. A primitive IoC container could look like that:

public function createRegisterController()
{
    $controller = new RegisterController();
    $controller->setImage($this->getImageService());
    // ...
    return $controller;
}
public function getImageService()
{
    if ($this->imageService === null) {
        $this->imageService = new Image();
        // inject dependencies of Image here
    }
    return $this->imageService;
}

The important point here is: Only inject the dependencies that are needed. And don't create a bunch of global variables disguised as DI.