Controllers

Overview

Controllers are the coordinators in MINIs MVC architecture. They:

Receive and process user requests
Interact with models to fetch/modify data
Load views to display responses
Handle form submissions and redirects

Every controller extends the base Controller class, which provides database access and model loading.

Base Controller Class

All controllers inherit from this base class:

application/core/controller.php

class Controller
{
    /**
     * @var null Database Connection
     */
    public $db = null;
    
    /**
     * @var null Model
     */
    public $model = null;
    
    /**
     * Whenever controller is created, open a database connection
     * and load "the model".
     */
    function __construct()
    {
        $this->openDatabaseConnection();
        $this->loadModel();
    }
    
    /**
     * Open the database connection with credentials from config.php
     */
    private function openDatabaseConnection()
    {
        $options = array(
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_OBJ,
            PDO::ATTR_ERRMODE => PDO::ERRMODE_WARNING
        );
        
        $this->db = new PDO(
            DB_TYPE . ':host=' . DB_HOST . ';dbname=' . DB_NAME . ';charset=' . DB_CHARSET,
            DB_USER,
            DB_PASS,
            $options
        );
    }
    
    /**
     * Loads the "model".
     */
    public function loadModel()
    {
        require APP . 'model/model.php';
        $this->model = new Model($this->db);
    }
}

What This Provides

$this->db - Direct database access

A PDO database connection configured with:

Fetch mode: PDO::FETCH_OBJ (results as objects)
Error mode: PDO::ERRMODE_WARNING (shows SQL errors)

Use this for custom queries:

$sql = "SELECT * FROM users WHERE active = 1";
$query = $this->db->prepare($sql);
$query->execute();
$users = $query->fetchAll();

$this->model - Model instance

An instance of the Model class with database access:

$songs = $this->model->getAllSongs();
$this->model->addSong('Artist', 'Track', 'URL');

Creating a Controller

Basic Structure

Create a new file in application/controller/:

application/controller/home.php

class Home extends Controller
{
    /**
     * PAGE: index
     * Handles http://yourproject/home/index (default page)
     */
    public function index()
    {
        // Load views
        require APP . 'view/_templates/header.php';
        require APP . 'view/home/index.php';
        require APP . 'view/_templates/footer.php';
    }
    
    /**
     * PAGE: exampleone
     * Handles http://yourproject/home/exampleone
     */
    public function exampleOne()
    {
        require APP . 'view/_templates/header.php';
        require APP . 'view/home/example_one.php';
        require APP . 'view/_templates/footer.php';
    }
}

Naming Conventions

Critical: Don’t use the same name for class and method. This triggers the class constructor:

// WRONG - triggers __construct behavior
class Home extends Controller
{
    public function home() { }  // Bad!
}

// CORRECT
class Home extends Controller
{
    public function index() { }  // Good!
}

See PHP Constructor Documentation

File and class names:

File: songs.php → Class: Songs
File: user_admin.php → Class: User_admin
Always match the filename (case-insensitive)

Real-World Controller Examples

Simple Page Controller

The Home controller displays static pages:

application/controller/home.php

class Home extends Controller
{
    public function index()
    {
        require APP . 'view/_templates/header.php';
        require APP . 'view/home/index.php';
        require APP . 'view/_templates/footer.php';
    }
    
    public function exampleOne()
    {
        require APP . 'view/_templates/header.php';
        require APP . 'view/home/example_one.php';
        require APP . 'view/_templates/footer.php';
    }
    
    public function exampleTwo()
    {
        require APP . 'view/_templates/header.php';
        require APP . 'view/home/example_two.php';
        require APP . 'view/_templates/footer.php';
    }
}

CRUD Controller

The Songs controller demonstrates full CRUD operations:

application/controller/songs.php

class Songs extends Controller
{
    /**
     * PAGE: index
     * URL: /songs or /songs/index
     * Display all songs
     */
    public function index()
    {
        // Fetch data from model
        $songs = $this->model->getAllSongs();
        $amount_of_songs = $this->model->getAmountOfSongs();
        
        // Variables are now available in views
        require APP . 'view/_templates/header.php';
        require APP . 'view/songs/index.php';
        require APP . 'view/_templates/footer.php';
    }
    
    /**
     * ACTION: addSong
     * URL: /songs/addsong
     * Process form submission to add a song
     */
    public function addSong()
    {
        if (isset($_POST["submit_add_song"])) {
            $this->model->addSong(
                $_POST["artist"],
                $_POST["track"],
                $_POST["link"]
            );
        }
        
        // Redirect back to index
        header('location: ' . URL . 'songs/index');
    }
    
    /**
     * ACTION: deleteSong
     * URL: /songs/deletesong/5
     * Delete a song by ID
     */
    public function deleteSong($song_id)
    {
        if (isset($song_id)) {
            $this->model->deleteSong($song_id);
        }
        
        header('location: ' . URL . 'songs/index');
    }
    
    /**
     * PAGE: editSong
     * URL: /songs/editsong/5
     * Display edit form for a song
     */
    public function editSong($song_id)
    {
        if (isset($song_id)) {
            // Fetch song data
            $song = $this->model->getSong($song_id);
            
            // Display edit form with $song data
            require APP . 'view/_templates/header.php';
            require APP . 'view/songs/edit.php';
            require APP . 'view/_templates/footer.php';
        } else {
            header('location: ' . URL . 'songs/index');
        }
    }
    
    /**
     * ACTION: updateSong
     * URL: /songs/updatesong
     * Process form submission to update a song
     */
    public function updateSong()
    {
        if (isset($_POST["submit_update_song"])) {
            $this->model->updateSong(
                $_POST["artist"],
                $_POST["track"],
                $_POST["link"],
                $_POST['song_id']
            );
        }
        
        header('location: ' . URL . 'songs/index');
    }
    
    /**
     * AJAX ACTION: ajaxGetStats
     * URL: /songs/ajaxgetstats
     * Return data for AJAX request
     */
    public function ajaxGetStats()
    {
        $amount_of_songs = $this->model->getAmountOfSongs();
        
        // Simple API response
        echo $amount_of_songs;
    }
}

Controller Method Patterns

1. Display Page (GET)

Fetch data and render views:

public function index()
{
    // 1. Fetch data from model
    $songs = $this->model->getAllSongs();
    $amount = $this->model->getAmountOfSongs();
    
    // 2. Load views (variables automatically available)
    require APP . 'view/_templates/header.php';
    require APP . 'view/songs/index.php';
    require APP . 'view/_templates/footer.php';
}

2. Process Form (POST)

Handle form submission and redirect:

public function addSong()
{
    // 1. Check if form was submitted
    if (isset($_POST["submit_add_song"])) {
        // 2. Process data (validation should go here)
        $this->model->addSong(
            $_POST["artist"],
            $_POST["track"],
            $_POST["link"]
        );
    }
    
    // 3. Redirect to prevent form resubmission
    header('location: ' . URL . 'songs/index');
}

POST-Redirect-GET pattern: After processing a POST request, always redirect to prevent duplicate submissions when users refresh the page.

3. Action with Parameter (GET/DELETE)

Process URL parameters:

public function deleteSong($song_id)
{
    // 1. Validate parameter exists
    if (isset($song_id)) {
        // 2. Cast to correct type for safety
        $song_id = (int) $song_id;
        
        // 3. Perform action
        $this->model->deleteSong($song_id);
    }
    
    // 4. Redirect
    header('location: ' . URL . 'songs/index');
}

4. AJAX Endpoint (JSON Response)

Return data for AJAX calls:

public function ajaxGetStats()
{
    $data = array(
        'song_count' => $this->model->getAmountOfSongs(),
        'last_updated' => time()
    );
    
    // Return JSON
    header('Content-Type: application/json');
    echo json_encode($data);
}

Call from JavaScript:

$.ajax({
    url: url + "songs/ajaxgetstats",
    type: "GET",
    success: function(data) {
        console.log("Songs:", data.song_count);
    }
});

Accessing Database and Models

Through the Model

Preferred approach for reusable queries:

public function index()
{
    // Use model methods
    $songs = $this->model->getAllSongs();
    $count = $this->model->getAmountOfSongs();
}

Direct Database Access

For one-off or complex queries:

public function customQuery()
{
    $sql = "SELECT * FROM song WHERE artist LIKE :search";
    $query = $this->db->prepare($sql);
    $query->execute([':search' => '%' . $_GET['q'] . '%']);
    $results = $query->fetchAll();
    
    // ... load views with $results ...
}

Passing Data to Views

Variables defined in the controller are automatically available in required views:

public function index()
{
    // Define variables
    $songs = $this->model->getAllSongs();
    $amount_of_songs = $this->model->getAmountOfSongs();
    $page_title = "All Songs";
    
    // Load view
    require APP . 'view/songs/index.php';
    
    // Inside index.php, use:
    // <?php echo $page_title; ?>
    // <?php foreach ($songs as $song) { ... } ?>
}

Views are included with require, so they share the same variable scope. Be careful not to accidentally override controller variables in views.

Redirecting

Use PHP’s header() function:

// Redirect to another page
header('location: ' . URL . 'songs/index');

// Redirect with query parameters
header('location: ' . URL . 'songs/index?success=1');

// Always exit after redirect to stop execution
header('location: ' . URL . 'songs');
exit;

Best Practices

1. Keep controllers thin

Move business logic to models:

// Bad: Logic in controller
public function addSong()
{
    if (strlen($_POST['artist']) < 3) {
        $error = "Artist name too short";
    }
    if (!filter_var($_POST['link'], FILTER_VALIDATE_URL)) {
        $error = "Invalid URL";
    }
    // More validation...
}

// Good: Logic in model
public function addSong()
{
    $result = $this->model->addSong(
        $_POST['artist'],
        $_POST['track'],
        $_POST['link']
    );
    
    if (!$result['success']) {
        // Handle error
    }
}

2. Validate input

Always validate and sanitize user input:

public function deleteSong($song_id)
{
    // Cast to integer
    $song_id = (int) $song_id;
    
    // Validate it's positive
    if ($song_id <= 0) {
        header('location: ' . URL . 'songs');
        exit;
    }
    
    $this->model->deleteSong($song_id);
    header('location: ' . URL . 'songs');
}

3. Use meaningful method names

// Good
public function editSong($song_id) { }
public function updateSong() { }
public function deleteSong($song_id) { }

// Unclear
public function action1() { }
public function doStuff() { }

4. Don't mix display and action methods

// editSong() displays the form
public function editSong($song_id)
{
    $song = $this->model->getSong($song_id);
    require APP . 'view/songs/edit.php';
}

// updateSong() processes the form
public function updateSong()
{
    $this->model->updateSong(/* ... */);
    header('location: ' . URL . 'songs');
}

Common Patterns

Check Authentication

public function adminPanel()
{
    if (!isset($_SESSION['user_logged_in'])) {
        header('location: ' . URL . 'login');
        exit;
    }
    
    // Show admin panel
    require APP . 'view/admin/panel.php';
}

Flash Messages

// Set message
public function addSong()
{
    $this->model->addSong(/* ... */);
    $_SESSION['success'] = "Song added successfully!";
    header('location: ' . URL . 'songs');
}

// Display in view
<?php if (isset($_SESSION['success'])): ?>
    <div class="alert"><?php echo $_SESSION['success']; ?></div>
    <?php unset($_SESSION['success']); ?>
<?php endif; ?>

Routing

How URLs map to controller methods

Models

Data layer and database operations

Views

Rendering HTML output

Architecture

Understanding the MVC pattern

Get Started

Core Concepts

Guides

Deployment

Controllers

Overview

Base Controller Class

What This Provides

Creating a Controller

Basic Structure

Naming Conventions

Real-World Controller Examples

Simple Page Controller

CRUD Controller

Controller Method Patterns

1. Display Page (GET)

2. Process Form (POST)

3. Action with Parameter (GET/DELETE)

4. AJAX Endpoint (JSON Response)

Accessing Database and Models

Through the Model

Direct Database Access

Passing Data to Views

Redirecting

Best Practices

Common Patterns

Check Authentication

Flash Messages

Routing

Models

Views

Architecture

Build docs developers (and LLMs) love

Get Started

Core Concepts

Guides

Deployment

​Overview

​Base Controller Class

​What This Provides

​Creating a Controller

​Basic Structure

​Naming Conventions

​Real-World Controller Examples

​Simple Page Controller

​CRUD Controller

​Controller Method Patterns

​1. Display Page (GET)

​2. Process Form (POST)

​3. Action with Parameter (GET/DELETE)

​4. AJAX Endpoint (JSON Response)

​Accessing Database and Models

​Through the Model

​Direct Database Access

​Passing Data to Views

​Redirecting

​Best Practices

​Common Patterns

​Check Authentication

​Flash Messages

​Related Documentation

Routing

Models

Views

Architecture

Build docs developers (and LLMs) love

Overview

Base Controller Class

What This Provides

Creating a Controller

Basic Structure

Naming Conventions

Real-World Controller Examples

Simple Page Controller

CRUD Controller

Controller Method Patterns

1. Display Page (GET)

2. Process Form (POST)

3. Action with Parameter (GET/DELETE)

4. AJAX Endpoint (JSON Response)

Accessing Database and Models

Through the Model

Direct Database Access

Passing Data to Views

Redirecting

Best Practices

Common Patterns

Check Authentication

Flash Messages

Related Documentation