OOP Review & Backend Patterns

OOP recap — putting it together

Real apps combine classes, interfaces, and namespaces. Keep models (data), services (logic), and controllers (HTTP) separate.

Real-life example: OOP in a web app is a restaurant — models are ingredients, services are chefs, controllers are waiters taking orders.

<?php
class CourseService {
  public function __construct(private PDO $db) {}

  public function findAll(): array {
    return $this->db
      ->query("SELECT id, title FROM courses")
      ->fetchAll(PDO::FETCH_ASSOC);
  }
}
?>

When to use OOP in PHP

Use classes for anything with state and behavior — users, orders, mailers. Small scripts can stay procedural.

Real-life example: A one-line hello.php does not need OOP. A student portal with login, courses, and payments does.

• Use type hints and return types everywhere
• Prefer dependency injection over global state
• Interfaces make testing and swapping implementations easy
• Next up: MySQL — store your objects in a database