Принцип открытости/закрытости

<?php
enum Products
{
    case SHIRT;
    case TSHIRT;
    case PANT;
}

class DiscountCalculator {
    private Products $product_type;
    private float $cost = 0;

    public function __construct(Products $product_type, float $cost = 0) {
        $this->product_type = $product_type;
        $this->cost = $cost;
    }

    public function get_discounted_price() {
        if ($this->product_type === Products::SHIRT) {
            return $this->cost - ($this->cost * 0.10);
        }
        if ($this->product_type === Products::TSHIRT) {
            return $this->cost - ($this->cost * 0.15);
        }

        if ($this->product_type === Products::PANT) {
            return $this->cost - ($this->cost * 0.25);
        }
    }
}

$dc_shirt = new DiscountCalculator(Products::SHIRT, 100)
echo $dc_shirt->get_discounted_price() . PHP_EOL;

$dc_tshirt = new DiscountCalculator(Products::TSHIRT, 100)
echo $dc_tshirt->get_discounted_price() . PHP_EOL;

$dc_pant = new DiscountCalculator(Products::PANT, 100)
echo $dc_pant->get_discounted_price() . PHP_EOL;

<?php
interface DiscountCalculator {
    public function get_discounted_price();
}

abstract class AbstractDiscountCalculator {
    protected float $cost = 0;

    public function __construct(float $cost = 0) {
        $this->cost = $cost;
    }
}

class DiscountCalculatorShirt extends AbstractDiscountCalculator implements DiscountCalculator {

    public function get_discounted_price() {
        return $this->cost * 0.9;
    }
}

class DiscountCalculatorTshirt extends AbstractDiscountCalculator implements DiscountCalculator {

    public function get_discounted_price() {
        return $this->cost * 0.85;
    }
}

class DiscountCalculatorPant extends AbstractDiscountCalculator implements DiscountCalculator {

    public function get_discounted_price() {
        return $this->cost * 0.75;
    }
}

$dc_shirt = new DiscountCalculatorShirt(100);
echo $dc_shirt->get_discounted_price() . PHP_EOL;

$dc_tshirt = new DiscountCalculatorTshirt(100);
echo $dc_tshirt->get_discounted_price() . PHP_EOL;

$dc_pant = new DiscountCalculatorPant(100);
echo $dc_pant->get_discounted_price() . PHP_EOL;

<?php
// Нарушение OCP — при добавлении фигуры нужно менять этот класс
class AreaCalculator {
    public function calculate(array $shape): float {
        if ($shape['type'] === 'circle') {
            return M_PI * $shape['radius'] ** 2;
        } elseif ($shape['type'] === 'rectangle') {
            return $shape['width'] * $shape['height'];
        }
        return 0;
    }
}

// Вызов
$calc = new AreaCalculator();
echo $calc->calculate(['type' => 'circle', 'radius' => 5]) . PHP_EOL;
echo $calc->calculate(['type' => 'rectangle', 'width' => 4, 'height' => 6]) . PHP_EOL;

<?php
// Нарушение OCP
class DataExporter {
    public function export(array $data, string $format): string {
        if ($format === 'json') {
            return json_encode($data, JSON_UNESCAPED_UNICODE);
        } elseif ($format === 'csv') {
            $handle = fopen('php://memory', 'r+');
            fputcsv($handle, array_keys($data[0]));
            foreach ($data as $row) {
                fputcsv($handle, $row);
            }
            rewind($handle);
            return stream_get_contents($handle);
        }
        return '';
    }
}

// Вызов
$exporter = new DataExporter();
$records = [['name' => 'Анна', 'age' => 30], ['name' => 'Иван', 'age' => 25]];
echo $exporter->export($records, 'json') . PHP_EOL;
echo $exporter->export($records, 'csv');

<?php
// Нарушение OCP
class NotificationService {
    public function send(string $channel, string $recipient, string $message): void {
        if ($channel === 'email') {
            echo "Email → {$recipient}: {$message}\n";
        } elseif ($channel === 'sms') {
            echo "SMS → {$recipient}: {$message}\n";
        }
    }
}

// Вызов
$service = new NotificationService();
$service->send('email', '[email protected]', 'Ваш заказ подтверждён');
$service->send('sms', '+79001234567', 'Код подтверждения: 1234');

<?php
// Нарушение OCP
class Sorter {
    public function sort(array $data, string $algorithm): array {
        if ($algorithm === 'bubble') {
            $arr = $data;
            $n = count($arr);
            for ($i = 0; $i < $n; $i++) {
                for ($j = 0; $j < $n - $i - 1; $j++) {
                    if ($arr[$j] > $arr[$j + 1]) {
                        [$arr[$j], $arr[$j + 1]] = [$arr[$j + 1], $arr[$j]];
                    }
                }
            }
            return $arr;
        } elseif ($algorithm === 'builtin') {
            sort($data);
            return $data;
        }
        return $data;
    }
}

// Вызов
$sorter = new Sorter();
$numbers = [5, 3, 8, 1, 9, 2];
print_r($sorter->sort($numbers, 'bubble'));
print_r($sorter->sort($numbers, 'builtin'));

<?php
// Нарушение OCP
class PaymentProcessor {
    public function pay(string $method, float $amount): void {
        if ($method === 'card') {
            echo "Оплата картой: {$amount} руб.\n";
        } elseif ($method === 'crypto') {
            echo "Оплата криптовалютой: {$amount} руб.\n";
        }
    }
}

// Вызов
$processor = new PaymentProcessor();
$processor->pay('card', 1500.0);
$processor->pay('crypto', 3200.0);