الوراثة، الواجهات، السمات والأصناف المجرّدة

<?php

declare(strict_types=1);

abstract class Exporter
{
    public function export(array $rows): string
    {
        return $this->head() . $this->body($rows);
    }

    abstract protected function head(): string;

    abstract protected function body(
        array $rows
    ): string;
}

final class CsvExporter extends Exporter
{
    protected function head(): string
    {
        return "id;name\n";
    }

    protected function body(array $rows): string
    {
        $lines = array_map(
            fn (array $r): string => implode(';', $r),
            $rows,
        );

        return implode("\n", $lines);
    }
}

$csv = new CsvExporter();
echo $csv->export([[1, 'Ada'], [2, 'Linus']]);

<?php

declare(strict_types=1);

interface Cache
{
    public function get(string $key): ?string;

    public function set(
        string $key,
        string $value
    ): void;
}

final class ArrayCache implements Cache
{
    private array $items = [];

    public function get(string $key): ?string
    {
        return $this->items[$key] ?? null;
    }

    public function set(
        string $key,
        string $value
    ): void {
        $this->items[$key] = $value;
    }
}

$cache = new ArrayCache();
$cache->set('lang', 'PHP');
echo $cache->get('lang');

<?php

declare(strict_types=1);

trait FileLogger
{
    public function log(string $message): void
    {
        echo "[file] $message\n";
    }
}

trait AuditLogger
{
    public function log(string $message): void
    {
        echo "[audit] $message\n";
    }
}

final class PaymentService
{
    use FileLogger, AuditLogger {
        FileLogger::log insteadof AuditLogger;
        AuditLogger::log as audit;
    }
}

$service = new PaymentService();
$service->log('Payment received');
$service->audit('Payment received');