README

FastForward\Clock provides PSR-20 compliant clock implementations and seamless integration with Fast Forward Container.

This package offers two clock implementations: SystemClock for production time and FrozenClock for deterministic testing.

✨ Features

🕒 PSR-20 Compliant - Full support for the PSR-20 Clock interface
🧪 Testing Made Easy - FrozenClock lets you freeze time for reliable tests
🌐 Timezone Support - Configure timezones in production and tests
🔌 Container Integration - Automatic service registration via ClockServiceProvider
🎯 Beginner Friendly - Simple API designed for developers new to PSR patterns

📦 Installation

composer require fast-forward/clock

Requirements:

PHP 8.3 or higher
fast-forward/container 1.6 or higher
psr/clock 1.0

🛠️ Usage

Basic: Get the current time

The simplest way to get the current time is using SystemClock:

<?php

declare(strict_types=1);

use FastForward\Clock\SystemClock;

$clock = new SystemClock();

echo $clock->now()->format(DATE_ATOM) . PHP_EOL;

With a specific timezone

<?php

declare(strict_types=1);

use FastForward\Clock\SystemClock;

$clock = new SystemClock('America/Sao_Paulo');

echo $clock->now()->format('Y-m-d H:i:s P') . PHP_EOL;

Using with Fast Forward Container

For larger applications, use the service provider to register the clock in your container:

<?php

declare(strict_types=1);

use FastForward\Clock\ServiceProvider\ClockServiceProvider;
use Psr\Clock\ClockInterface;
use function FastForward\Container\container;

$container = container(new ClockServiceProvider());

$clock = $container->get(ClockInterface::class);

echo $clock->now()->format(DATE_ATOM) . PHP_EOL;

Freezing time for tests

Use FrozenClock to create deterministic tests:

<?php

declare(strict_types=1);

use FastForward\Clock\FrozenClock;

$clock = new FrozenClock('2026-04-07 10:00:00');

echo $clock->now()->format(DATE_ATOM) . PHP_EOL;
// Output: 2026-04-07T10:00:00+00:00

FrozenClock accepts multiple input formats:

<?php

declare(strict_types=1);

use FastForward\Clock\FrozenClock;

// From a DateTimeImmutable
$clock1 = new FrozenClock(new DateTimeImmutable('2026-04-07 10:00:00'));

// From a string
$clock2 = new FrozenClock('next Monday');

// From a timestamp
$clock3 = new FrozenClock(1775640000);

// From another ClockInterface
$clock4 = new FrozenClock(new SystemClock('America/New_York'));

Using FrozenClock with Fast Forward Container in tests

<?php

declare(strict_types=1);

use FastForward\Clock\ServiceProvider\ClockServiceProvider;
use FastForward\Clock\FrozenClock;
use FastForward\Container\ServiceProvider\ArrayServiceProvider;
use Psr\Clock\ClockInterface;
use Psr\Container\ContainerInterface;
use function FastForward\Container\container;

$frozenClock = new FrozenClock('2026-04-07 10:00:00');

$testProvider = new ArrayServiceProvider([
    FrozenClock::class => static fn(ContainerInterface $container): FrozenClock => $frozenClock,
    ClockInterface::class => static fn(ContainerInterface $container): FrozenClock => $container->get(FrozenClock::class),
]);

$container = container($testProvider, new ClockServiceProvider());

$clock = $container->get(ClockInterface::class);

echo $clock->now()->format(DATE_ATOM) . PHP_EOL;

🧰 API Summary

Class	Description
`FastForward\Clock\SystemClock`	PSR-20 clock that returns current system time with optional timezone
`FastForward\Clock\FrozenClock`	PSR-20 clock that returns a fixed time (ideal for testing)
`FastForward\Clock\ServiceProvider\ClockServiceProvider`	Registers clock services in Fast Forward Container

SystemClock Constructor

public function __construct(DateTimeZone|string|null $timezone = null)

Parameter	Type	Description
`$timezone`	`DateTimeZone\|string\|null`	Timezone for the clock (defaults to system default)

FrozenClock Constructor

public function __construct(DateTimeInterface|ClockInterface|string|int|float $clock = 'now')

Parameter	Type	Description
`$clock`	`DateTimeInterface\|ClockInterface\|string\|int\|float`	The time to freeze. Accepts DateTimeImmutable, string (relative or absolute), timestamp, or another ClockInterface

🔌 Integration

This package integrates seamlessly with:

Fast Forward Container - Use ClockServiceProvider for automatic registration
PSR-20 - Both SystemClock and FrozenClock implement Psr\Clock\ClockInterface
Any PSR-11 Container - Both clocks can be instantiated directly without the service provider

📁 Directory Structure

src/
├── SystemClock.php              # Production clock implementation
├── FrozenClock.php              # Testing clock implementation
├── ServiceProvider/
│   ├── ClockServiceProvider.php # Container service provider
│   └── Factory/
│       └── DateTimeZoneFactory.php # Timezone factory
tests/
├── SystemClockTest.php
├── FrozenClockTest.php
└── ServiceProvider/
    └── ClockServiceProviderTest.php
examples/
├── 01-system-clock.php
├── 02-system-clock-with-timezone.php
├── 03-frozen-clock.php
├── 04-frozen-clock-inputs.php
├── 05-frozen-clock-container.php
└── 06-psr20-clock-interface.php
docs/
└── ... (Sphinx documentation)

⚙️ Advanced / Customization

Custom timezone via configuration

If you use Fast Forward Config, you can configure the default timezone:

<?php

use FastForward\Config\Config;
use FastForward\Clock\ServiceProvider\ClockServiceProvider;
use function FastForward\Container\container;

$config = new Config([
    DateTimeZone::class => 'America/Sao_Paulo',
]);

$container = container($config, new ClockServiceProvider());

Creating a custom clock

Both clocks are final readonly classes, but you can wrap them:

<?php

declare(strict_types=1);

use FastForward\Clock\FrozenClock;
use Psr\Clock\ClockInterface;

final class StubbedClock implements ClockInterface
{
    public function __construct(private ClockInterface $clock)
    {
    }

    public function now(): \DateTimeImmutable
    {
        return $this->clock->now();
    }

    public static function create(string $time): self
    {
        return new self(new FrozenClock($time));
    }
}

❓ FAQ

Q: What's the difference between SystemClock and FrozenClock?
A: SystemClock returns the current time and is suitable for production. FrozenClock returns a fixed time and is ideal for testing.

Q: Which interface should I use in my application?
A: Use Psr\Clock\ClockInterface for maximum portability. Both implementations satisfy this interface.

Q: How do I freeze time in tests?
A: Use FrozenClock directly, or register it via ArrayServiceProvider before ClockServiceProvider.

Q: Can I use this without Fast Forward Container?
A: Yes! Simply instantiate SystemClock or FrozenClock directly in your code.

Q: Does this work with other PSR-11 containers?
A: Yes. The clocks are standalone classes that don't require any container.

Q: How do I set a specific timezone?
A: Pass a timezone string or DateTimeZone instance to the SystemClock constructor.

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