Stephen Stephen - 1 year ago 66
PHP Question

What does $model->save() do in PHP Yii?

I have a couple quick conceptual questions about saving models in PHP's Yii framework. I've run into this code a couple of times $model->save() (for example if($model->save())....

but I've never quite understood what it means.

Also, I read in the MVC Tips/Handbook that we should try to save our models in the model and not the controller - could someone explain why that is? I have a friend who has told me that it doesn't matter - but, I'd like to understand the rule behind it.

Thank you for you help!

Answer Source

What does $model->save() do?

Just check the source, it's on github. Apply logic, and the answer is pretty predictable.

As the docs clearly state: the BaseActiveRecord represents a data object. It could be a row returned from a MySQL query, or a processed form being sent by a client, or a MongoDB document, or whatever.
Calling save on that object either inserts the data into the DB you chose, or attempts to update that record. Depending on the insert/update call being successful, it returns a boolean (true if save succeeded, false if it failed).

It's pretty intuitive, really. If you want to learn more about the tools/frameworks you are using, common sense dictates you check out their online documentation. Yii's docs seem to me to be pretty comprehensive and easy to navigate: check them here.

Why save models in the Model?

Well that's easy, but it requires some disambiguation. The term "model" is often used to refer to the data containers. The objects on which you call save in this case. They are data models, true enough, and they are used to carry data back and forth throughout your application. In Yii, what some call models are called "ActiveRecords".

In the acronym MVC (as you know Model View Controller), the Model part actually covers a lot more than mere data containers. That "Model" (with a capital M) refers to the Model layer, also known as the logic or business layer. It's the part of your application that actually will contain the bulk of the code. It's there where the more complex computation is handled, it's the layer where you'll connect and query the DB. And it's this layer that has methods that the controller will call. These methods will then return data models (lower-case m) containing the data or the result of the computation that the controller will then pass on to the view.
If you want to know what logic/jobs/classes make up the Model layer, simply ask yourself this simple question: "What doesn't this bit of do?" If it doesn't handle the raw request, and it doesn't present the data to the user (those are the jobs of the controller and the view respectively), it's part of the Model layer, with the exception of a router component, dispatcher and all that that ties an MVC framework together, of course.

Controller actions (the methods in a controller, obviously) should, therefore be quite small. All they really do, 9/10 times, is pour the request data (form submissions and the like) into a model, and call one or more methods on a service (which is part of the Model layer). These methods will receive the models created in the controller as arguments, and set to work with them.
The controller can perform some basic validation, but the Model layer will dot the i's and cross the t's.

Once the Model layer has done its job, it's back to the controller which has only two things left to do: Did the Model layer return data that it expects or not? If so, pass it on to the view. If not (an exception was thrown or nothing was returned) -> handle the error/exception and, if required, redirect the user.

So in short: The Model layer is the bulk of your code, and it communicates with the controller (and internally) through data models. The Model layer never communicates with the view directly, nor does it redirect the user or handles raw input like $_POST data.

Here's a couple of links to posts of mine where I explain this even further, complete with graphs and what not. They are code-review answers, so ignore the bits that deal with the code itself, but the background information may be relevant to you:

CodeReview: How to put XML results in the MVC pattern?
CodeReview: PHP MVC: how to do $_POST the right way

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