I want to override the guestbook functionality. To be exact, I want to override the action_form_save_entry() function on [mysite]/concrete5/core/controllers/blocks/guestbook.php
I've tried to override it these ways:
noe of them works. I can't find any way how to override that file. The documentation here and here doesn't show how to override that /core/ directory. Their forum never helps. Google result also just get misled with the 'core' keyword. All the result just take the 'core' meaning as just what's exist on the /concrete5/ directory, not the exact true /concrete5/core
Looks like that /concrete5/core/ directory appear only on the newer version. CMIIW.
Btw, maybe I should also tell you what I want to do with that function. Probably you have another workaround for this instead of simply overriding it. I want to add SMS notification functionality to it. So whenever someone submit a new comment, an SMS would be sent to the admin of a particular page.
Yes, the /concrete/core directory structure is new to 5.6. Tutorials and documentation on c5 can be ... lacking ... but in this case it's just a matter of them being behind a bit.
The "real" guestbook controller is at /concrete/blocks/guestbook/controller.php. You'll notice that it's just a shell of a class:
class GuestbookBlockController extends Concrete5_Controller_Block_Guestbook {}
The file that you referenced defines Concrete5_Controller_Block_Guestbook.
So, the solution is to override the real controller, not whatever it extends (ie, the file that you were looking at). Thinking in this way, it should be clearer that you need to create a file at /blocks/guestbook/controller.php. In fact, just copy the controller.php that I referenced above because you need to keep the (sometimes multiple) classes. Then, you can override the particular function. (Don't forget to call parent::action_save_form_entry()).