为什么控制器需要访问Web PHP MVC中的模型？

Question

Why wouldn't MVC not work just fine if the controller would only have access to the view (diagram #2 in the image below) and the view would have access to the model?

On most sites (some topics on Stack Overflow included), I have read that it's should be like shown in the left diagram (diagram #1 in the image below).

I have added an image, just so that you can understand my question better (don't mind that this is a UML diagram, look at it just as an normal diagram).

NOTE: Of course there is an dataMapper to which one the model has access and an init and frontController above the controller, etc. But I didn't add them to the image just to keep it as simple as possible.

Answer 1

If it's about simply displaying data, then yes, the schematic should be that the controller invokes a view and the view gets data from the model to visualise its state.

However, oftentimes the controller triggers change in the model's state. E.g. a user asks to be logged in, a new entry is posted, an old entry is deleted, or any other kind of change that's triggered by incoming requests. The controller propagates those "write requests" to the appropriate model method and decides on what should be done further based on the outcome. The view is "read only", it's not its job to handle such things.