php-mvc | Project created in the course https | Learning library

I'd take this question rather as a genuine inquiry than a request to review some SEO spam article from Internet. So it goes:

What you need to understand in the first place is that the term "model" is ambiguous. It can represent either the whole application's business logic, or just what you meant - some piece of code that interacts with the database. To avoid this ambiguity, let's stick with the former. It will help you to settle with the Controller. Whereas we will call a "lesser model" a storage. A cover term for a code which actually interacts with the database.

I have a very concise writeup, MVC in simpler terms or the structure of a modern web-application. It will help you to wrap your head around MVC at whole.

Now closer to your question.

A database wrapper cannot be considered a model, in either meaning. A database wrapper is a service used by the storage class. So, you can have at least 3 layers in your application:

• a controller. Just an interface to convey an HTTP client's request to the business model
• a service or a helper. the code which is usually (and wrongly) written in the controller. For example, if you need to register a user, in the controller you are calling a method from a user service, providing the data came from the client.
• a storage class. The actual code to interact with a database. For example it could be a User class that contain methods such as register and such. This class would use PDO (or some more advanced wrapper, or an ORM instance) as a class variable.

Where the latter two should actually encapsulate your whole application's business logic.

The most tricky part here is the instantiation of the Storage class. Given the connection must be done only once, there should be means to instantiate the UserStorage object providing it with the database connection. That is slightly different issue which is solved by means of the Dependency Injection Container

To illustrate the above with a bit of code