MVC Architecture in PHP

MVC is acronym for Model View Controller. It is an architectural pattern standard. Instead of writing all the php code and html markup in one file we segregate it. So say in a typical MVC framework there will be three folders:

1. Model
2. View
3. Controller

Here is what each one of them will be doing

• The Model directory will contain the Models aka the php files containing all the database queries.
• Views folder will contain all the html markup templates.
• All the business logic will be placed in the Controller.

URL Pattern

A framework that follows the conventional MVC pattern has a fix pattern of url structure. This is of the form http://some-domain.com/{controller}/{method}/{params}.
So say we have a webpage that displays all the news articles from database then the url would be something like http://some-domain.com/news/all. Here news will be our controller, which means there will be a news.php file containing a class News in the Controller directory. And this class will have a method all.

Similarly the url for a single news article page will be something like http://some-domain.com/news/view/212. So in the same class news there will be another method view which accepts one parameter.

Controller

So below is how our news class contoller will be looking like.

Controller/news.php

Now as said earlier the controller contains only the business logic. All the database queries are handled by the model. So say to fetch all the news from database we won’t be writing the database query in the Controller. But instead this will go in our model.

Model

So in the Model directory there will be a file News_model.php

Model/news-model.php

query("SELECT * FROM news ORDER BY publish_date");
        return $all_news;
    }
}
?>

And our controller will just call this method to fetch all the news.

Controller/news.php

get_all_news();
        load_view('all-news',array('all_news'=>$all_news)); //this is equivalent to require_once('Views/all-news.php');
    }
}
?>

Views

The last line of the method uses load_view function. What this function will do is require_once the all-news.php file in the view folder and pass the $all_news variable to it. So this variable is available for use in the view file all-news.php.

Below is how our view file all-news.php would look like

Views/all-news.php

    
        

            
                

                    
title ?>
                    publish_date; ?>
                    
content ?>
                
            
        
    

So as can be seen from above code, the html markup is inserted in view file. It’s upto the controller to decide which view file to use.

Bootstraping

You must be eager to know how is it that automatically the controller class is called by the program. This is actually done using .htaccess and a bootstrap.php file.

.htaccess

    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteRule ^ bootstrap.php [L]

What the above code does is redirect all the requests to bootstrap.php file. So even if you go to http://some-domain.com/anything, you will be redirected to bootstrap.php. However in the address bar you’ll see http://some-domain.com/anything although it will be the bootstrap.php file that you’ll be viewing.

bootstrap.php

$request_url = $_SERVER['REQUEST_URI'];
$parts = explode('/', trim($request_url, '/'));
$controller = $parts[0];
$method = $parts[1];
$params = array_slice($parts,2); //remove first two elements aka controller & method

if( file_exists('Controller/'.$controller) ) {
    require_once('Controller/'.$controller.'.php');
    
    $controller_instance = new $controller;
    
    if( method_exists($controller,$method) ) {
        call_user_func( array( $controller_instance, $method ) );
    }
    else {
        die("Controller method does not exist");
    }
}
else {
    die("Controller file does not exist");
}

Routing

Nowadays modern MVC framworks provide a routing class that specifies which controller to be called for a particular url. In contrast to the conventional url patter
http://some-domain.com/{controller}/{method}/{params} we can have a different controller to handle a particular request using the routing class. Below is how a typical routing class looks like:

get('news/all',array('News','all'));
?>

Above is a generic example. The actual class and method name and the way of calling the methods may differ from framework to framework. But the conceptual idea remains the same. Its the router that determines which controller class will handle which request.

Summing it up

Advantages of using MVC Pattern

• In real world application you’ll never have only db query that fetches all news but instead dozens of them querying probably different db table.
• In an office team there would be a designer and more than one developer. A designer may or may not know php. Also two developers can’t work on same file simultaneously.
• Apart from querying database you would be doing lots of others stuffs like form validation, sending mails etc.
• You can have any url of your choice if you are using a MVC framwork with powerful routing. So like instead of http://some-domain.com/view-news.php?news_id=55 we can have http://some-domain.com/view-news/55. Ofcourse this can easily achieved using some rules in .htaccess file but with a framework this is extremely simple.
• As your application grows you’ll find a framework much more cleaner to maintain in the long run.

In this tutorials we have tried explaining the concept using an example. Please note that we haven’t tried to create a MVC framework but instead understand how these frameworks work.