PHP - Functions from the controller in view - php

Question

I'm trying to learn MVC pattern, (but without the models because I don't see for what I can use them when I have the controllers).
So I want to display some content in my view. How do I do that?
This is my controller that takes care of index:
<?php
class Index extends Controller {
function __construct() {
parent::__construct();
$this->view->render('mainpage/index');
}
public function wynik($arg) {
echo $arg;
}
}
$klasa = new Index();
?>
And I want to call the function wynik($arg) in my view. How can I do this? My Controller library looks like this:
<?php
class Controller {
function __construct() {
$this->view = new View();
}
}
?>
And in views/mainpage/index.php I'm trying something like this:
<?php
echo $klasa->wynik('abc');
// tried this too:
$this->wynik('abc');
?>
But it doesn't work:
Notice: Undefined variable: klasa in C:\wamp\www\lvc\views\mainpage\index.php on line 2
and
Fatal error: Call to a member function wynik() on a non-object in C:\wamp\www\lvc\views\mainpage\index.php on line 2
This is View library:
<?php
class View {
function __construct() {
}
public function render($name, $noInclude = false) {
if ($noInclude == true) {
require 'views/' . $name . '.php';
} else {
require 'views/header.php';
require 'views/' . $name . '.php';
require 'views/footer.php';
}
}
}
?>
I was thinking - yeah, it searches for wynik() function in View() class, that's why it errors. I want the view to search through functions in my controller. How can I do this?

Answer 1

This code example is not working because the variable $klasa does not exist when you are trying to reference it. The initialization of the object done by calling "new Index()" must be completed first, then that value will be assigned to $klasa. Thus, your code is trying to access $klasa before it exists.
That said, I wouldn't continue to debug this problem. You are missing the point of MVC entirely, and until you understand it, you will not be able to code a controller and view that work well together. Spend time understanding MVC, not by implementing it yourself, but by using another system as an example.
If PHP is your flavor, try the Yii, CodeIgniter or Symphony Frameworks. If you like Python, try Django. If you like Ruby, try Rails. If you like C, learn Objective-C and try iOS.
The MVC model is very simple:
Model- This is where your data is stored.
View- This is how your data is represented to a user.
Controller- This is what your view talks to, so that it can act on the model.
Let's use a simple ice cream vending machine as an example. Assume the vending machine is one of those machines is like this one, where you can't see the items:
Model- The ACTUAL ice creams stored in the back. Lets say, 4 chocolate, 1 strawberry, 3 vanilla. The view and controller don't care how much of each ice cream are there. It is the model's job to keep track of that and make sure we don't have negative ice creams in slots, or other things that don't make sene, for example.
View- These are the little buttons showing what ice creams exist as choices. The view doesn't know or care how many ice creams are in the back, or what ice creams even exist. It simply shows the user something relating to the model, and it doesn't care what is in the model or how the model is structured.
Controller- When a user interacts with the view (that is, they push a button) the controller will take that input and run it by the model. The controller doesn't care how the model is structured, it doesn't know what is back there. All it knows is "When a user presses a button, I need to use the data in the model to make a decision based on that input". For example, when the user presses on a valid item that is in stock, the controller takes that input, runs it by the model, sees that it is ok and dispenses an ice cream. When the user presses on an invalid item that is not in stock, the controller takes that input, runs it by the model, sees that it is out of stock, and tells the view to display an error.
If you get this basic concept down, MVC as a whole will make a lot more sense and speed up dev time dramatically. Understanding MVC is probably one of the more important things for a budding web/mobile developer right now, as most popular web frameworks are based on it (Django, Rails, Yii/CodeIgniter/Symphony), as well as iOS.

Answer 2

MVC is a design patter which combines two layers:
Model layer
Presentation layer
If your application does not have model layer (which contains all the domain business logic), then there is no MVC.
Presentation layer is made mostly from two groups of structures: views and controllers.
controllers : responsible for reacting to user's input and, based on that, changing the state of model layer and view.
views : responsible for the display(or presentation) logic, based information, that view has received from model layer. Based on this information views choose to appropriate response - it can be either just a HTTP header or HTML file, rendered from multiple template or formated JSON/XML data.
But you do not really have Views either. What you call "view" is actually are simple PHP templates.
As for the view accessing controller's methods, it is against all the principles in MVC and MVC-inspired patterns. View is a separate entity, which acquires data from model layer and has the state changed by controllers.
In classical MVC and Model2 MVC patterns the view is active. It requests the information directly from the model layer. Whereas in MVP and MVVM patterns the view is passive and information from model layer is provided by controllers (though in these patterns they are called "presenters" and "viewmodels" respectively).
Views do not use controllers.
Please, do some research before you start throwing terms around just because you think, that it is the latest thing.
Read the following materials:
GUI Architectures
MVC in PHP part 1: Hello World
Model-View-Confusion part 1: Why the model is accessed by the view in MVC
A Description of the Model-View-Controller User Interface Paradigm in the Smalltalk-80 System
How should a model be structured in MVC?

Answer 3

Instead of MVC and not really knowing why and so on, I suggest you another concept called Transaction Script that also work very well with a Frontend Controller or an Application Controller.
Working with Transaction Scripts allows you to get more familiar with OOP while you also benefit from some application structure without the overhead and problems that a misunderstood MVC does carry.
For example within a transaction script object, everything can access the functions of that a transaction. Your libraries, your view and everything else (the model).
Then you will see things growing. But forget Codeigniter and similar, write this from scratch (don't mimic things), you'll learn more and you will have more efficient code.
And you will have it your way, which is great for learning.
For the libraries, just fetch stuff from the Packagist and Pear repositories you will not have many wishes left.

Answer 4

I am not going to add code samples here, but I hope what I say will help you look in the right direction. LVC (Library, View, Controller) is just you changing one name(Model) to another (Library) Doesnt really matter at all, you are still using MVC, you just happen to call your Model a Library. This is a vast topic, but I am only trying to make you see the use of having models and offloading code into that instead of in controllers.
The way to look at it is like this:
Typically controllers should only perform following - check requests, invoke Model(In your case Library) methods, which process those requests, and take those results and pass to the view to render. Think of each function in a controller to be an endpoint URL that the user can type in the address bar and access.
Think you have a function like profile($user_id) in a controller called user, to show user profile and the user accesses it using the url www.mydomain/user/profile/1234.This is all very fine. But what happens if you start throwing in all kinds of utility functions inside this controller like say, strip_all_zeroes(). It becomes bad if the user can access this using mydomain.com/user/strip_all_zeroes, right? It might start throwing all kinds of warnings,errors, or even expose sensitive data..That is where models come in. They can be used to create all kinds of helper functions, whole data classes as required..
Of course this is very broad, over-simplified and not totally accurate, but I hope you get the idea..