BoShurik

interface BalanceInterface
{
    public function get();

    public function inc($value);

    public function dec($value);
}

class Balance implements BalanceInterface
{
    private $value;

    public function get()
    {
        return $this->value;
    }

    public function inc($value)
    {
        $this->value += $value;
    }

    public function dec($value)
    {
        $this->value -= $value;
    }
}

class CacheBalance implements BalanceInterface
{
    /**
     * @var BalanceInterface
     */
    private $next;

    /**
     * @var \Psr\Cache\CacheItemPoolInterface
     */
    private $cache;

    public function __construct(BalanceInterface $next, \Psr\Cache\CacheItemPoolInterface $cache)
    {
        $this->next = $next;
        $this->cache = $cache;
    }

    public function get()
    {
        $item = $this->cache->getItem('balance');
        if ($item->isHit()) {
            return $item->get();
        }

        $value = $this->next->get();

        $item->set($value);
        $this->cache->save($item);

        return $value;
    }

    public function inc($value)
    {
        return $this->next->inc($value);
    }

    public function dec($value)
    {
        return $this->next->dec($value);
    }
}

class LogBalance implements BalanceInterface
{
    /**
     * @var BalanceInterface
     */
    private $next;
    /**
     * @var \Psr\Log\LoggerInterface
     */
    private $logger;

    public function __construct(BalanceInterface $next, \Psr\Log\LoggerInterface $logger)
    {
        $this->next = $next;
        $this->logger = $logger;
    }

    public function get()
    {
        return $this->next->get();
    }

    public function inc($value)
    {
        $this->logger->info(sprintf('Increase balance by %d', $value));

        return $this->next->inc($value);
    }

    public function dec($value)
    {
        $this->logger->info(sprintf('Decrease balance by %d', $value));

        return $this->next->dec($value);
    }
}

$initialBalance = new \Balance();
$cacheBalance = new \CacheBalance($initialBalance, $cache);
$logBalance = new \LogBalance($cacheBalance, $logger);

$balance = $logBalance;