Best Place for Validation in Model/View/Controller Model?
I am working on a PHP project which makes extensive use of the MVC design pattern. I am looking to add validation to a form and am curious as to what the right place for validation is.
Due to the way that forms are generated, validation on postback data is a lot simpler and less repetitive in view components. Is it acceptable to have the view validating response data, or should this be implemented within the controller, or even the model?
What are the benefits?
Answer
The right place for validation is the Model.
This makes most sense because you are doing validation on the data, which is what the model represents. In terms of the CRUD updates, the model should always be used somehow.
If you are changing data from the view, you should have validations being checked.
If you have controllers changing data, you should have validations being checked.
And finally if you have having the model itself changing data, you should still have validations.
The only way to achieve this state is to have the validation go into the model.
Due to performance and faster response, after implementing the validations in the model, you should try to add some sort of client side(JS) to immediately notify the end user.
Validation is always about the data. Why are you validating data? So you can keep the integrity of the information your storing. Having the validations at the model level allows data to theoretically be always correct. This is always a neccesity. From there you can add extra validations in your business logic and client side to make your application more user friendly.