Building a Simple MVC Application

A small MVC app can use a front controller, a dedicated service/model and a template.

What It Does and When to Use It

Separate business logic, input handling and rendering at a clearly identified boundary. Controllers translate HTTP input to operations; domain services implement rules; templates render escaped output.

Requirements, Inputs and Expected Behavior

Confirm the runtime, extension, environment variables, and permissions before running the examples in production. Avoid turning the controller into the place for SQL, validation and HTML construction.

Example 1: Basic Operation

Separate business logic, input handling and rendering at a clearly identified boundary.

<?php
final class UserRepository { public function find(int $id): array { return ['id'=>$id,'name'=>'Ava']; } }
final class UserController { public function __construct(private UserRepository $repo) {} public function show(int $id): array { return $this->repo->find($id); } }
echo json_encode((new UserController(new UserRepository()))->show(2), JSON_THROW_ON_ERROR);

Example 2: Behavior and Validation

Use the front controller to select responses while keeping routing separate from models.

<?php
$path=parse_url($_SERVER['REQUEST_URI']??'/',PHP_URL_PATH);
if ($path==='/health') { header('Content-Type: application/json'); echo json_encode(['status'=>'ok']); }
else { http_response_code(404); echo 'Not found'; }

Practical Example: Application Use

Render a trusted template path with controlled data; never derive template paths from user input.

<?php
function render(string $template, array $data): string {
    extract($data, EXTR_SKIP); ob_start();
    try { require $template; return (string)ob_get_clean(); }
    catch(Throwable $e) { ob_end_clean(); throw $e; }
}

Important Behavior and Edge Cases

The second example highlights: Use the front controller to select responses while keeping routing separate from models. The practical example adds: Render a trusted template path with controlled data; never derive template paths from user input.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• A small MVC app can use a front controller, a dedicated service/model and a template.
• Render a trusted template path with controlled data; never derive template paths from user input.
• Treat template names, route parameters and user data as separate trust domains.