接口 #

<?php
interface LoggerInterface
{
    public function log(string $message): void;
    public function error(string $message): void;
}

<?php
class FileLogger implements LoggerInterface
{
    public function log(string $message): void
    {
        file_put_contents('app.log', "[INFO] $message\n", FILE_APPEND);
    }
    
    public function error(string $message): void
    {
        file_put_contents('app.log', "[ERROR] $message\n", FILE_APPEND);
    }
}

<?php
interface Readable
{
    public function read(): string;
}

interface Writable
{
    public function write(string $data): void;
}

class FileHandler implements Readable, Writable
{
    public function read(): string
    {
        return file_get_contents('data.txt');
    }
    
    public function write(string $data): void
    {
        file_put_contents('data.txt', $data);
    }
}

<?php
interface Status
{
    public const ACTIVE = 1;
    public const INACTIVE = 0;
}

echo Status::ACTIVE;

<?php
interface LoggerInterface
{
    public function log(string $message): void;
    
    public function error(string $message): void
    {
        $this->log("[ERROR] $message");
    }
}

<?php
class UserService
{
    public function __construct(
        private LoggerInterface $logger
    ) {}
    
    public function create(array $data): User
    {
        $this->logger->log("Creating user");
        return new User($data);
    }
}

<?php
interface UserRepositoryInterface
{
    public function find(int $id): ?User;
    public function save(User $user): bool;
    public function delete(int $id): bool;
}

class MySqlUserRepository implements UserRepositoryInterface
{
    public function find(int $id): ?User
    {
        
    }
    
    public function save(User $user): bool
    {
        
    }
    
    public function delete(int $id): bool
    {
        
    }
}