README

Immutable PHP DTOs with bidirectional casting. No framework required. ~8x faster than the alternative.

Dt0 (DeeTO) is a PHP 8.2+ Data Transfer Object implementation that uses native readonly properties for true immutability. One #[Cast] attribute handles input transformation, output formatting, defaults, and property renaming. Compiled once per class, fast always.

Quick Start

use fab2s\Dt0\Dt0;
use fab2s\Dt0\Attribute\Cast;
use fab2s\Dt0\Caster\DateTimeCaster;
use fab2s\Dt0\Caster\DateTimeFormatCaster;

class UserDto extends Dt0
{
    public readonly int $id;
    public readonly string $name;
    public readonly string $email;

    #[Cast(
        in: DateTimeCaster::class,
        out: new DateTimeFormatCaster('Y-m-d'),
    )]
    public readonly DateTimeImmutable $createdAt;

    #[Cast(default: 'user')]
    public readonly string $role;
}

// Create from anything
$user = UserDto::make(id: 1, name: 'Jane', email: 'jane@example.com', createdAt: '2024-01-15');
$user = UserDto::fromArray($apiResponse);
$user = UserDto::fromJson($jsonString);

// Access properties
$user->name;       // 'Jane'
$user->createdAt;  // DateTimeImmutable instance
$user->role;       // 'user' (default applied)

// Output with casting applied
$user->toArray();  // [..., 'createdAt' => DateTimeImmutable, ...]
$user->toJson();   // {..., "createdAt": "2024-01-15", ...}

// Immutable updates
$admin = $user->update(role: 'admin');
$user->role;   // 'user' (unchanged)
$admin->role;  // 'admin' (new instance)

Installation

composer require fab2s/dt0

For Laravel model casting integration, see laravel-dt0.

Why Dt0

• Real immutability, enforced by PHP. Native readonly properties — accidental writes cause fatal errors, not silent bugs.
• One attribute to rule them all. #[Cast] handles input transformation, output formatting, defaults, and property renaming in a single, composable attribute.
• Framework-agnostic. Use anywhere PHP runs — including standalone validation powered by Laravel's validation engine, without the framework.
• Compiled once, fast always. Reflection and metadata processed once per class, then cached. ~8x faster than spatie/laravel-data for typical operations.

Creating Instances

Custom constructors with promoted properties are supported. See Creating Instances for constructors, new vs factory methods, and edge cases.

Casting

Dt0 supports bidirectional casting: transform values on the way in (hydration) and out (serialization).

use fab2s\Dt0\Attribute\Cast;
use fab2s\Dt0\Caster\DateTimeCaster;
use fab2s\Dt0\Caster\DateTimeFormatCaster;
use fab2s\Dt0\Caster\ScalarCaster;
use fab2s\Dt0\Caster\ScalarType;

class ArticleDto extends Dt0
{
    public readonly string $title;

    #[Cast(in: new ScalarCaster(ScalarType::int))]
    public readonly int $viewCount;

    #[Cast(
        in: DateTimeCaster::class,
        out: new DateTimeFormatCaster(DateTimeFormatCaster::ISO),
    )]
    public readonly DateTimeImmutable $publishedAt;
}

$article = ArticleDto::make(
    title: 'Hello World',
    viewCount: '42',           // string -> int
    publishedAt: '2024-01-15', // string -> DateTimeImmutable
);

Class-level casting with #[Casts]:

#[Casts(
    status: new Cast(default: 'pending'),
    priority: new Cast(default: 0),
    createdAt: new Cast(in: DateTimeCaster::class),
)]
class TaskDto extends Dt0
{
    public readonly string $title;
    public readonly string $status;
    public readonly int $priority;
    public readonly DateTime $createdAt;
}

Built-in types — Enums and nested Dt0 classes are handled automatically, no caster needed:

class OrderDto extends Dt0
{
    public readonly Status $status;      // BackedEnum — auto-cast from string/int
    public readonly AddressDto $address; // Nested Dt0 — auto-cast from array/JSON
}

Available Casters

See Casters Documentation for detailed usage, bidirectional casting, and custom casters.

Validation

Dt0 provides standalone validation powered by Laravel's validation engine — no Laravel framework required. In Laravel applications, it auto-detects the framework and uses Laravel's validator transparently.

Requires illuminate/validation and illuminate/translation (v11+):

composer require "illuminate/validation:^11.0|^12.0" "illuminate/translation:^11.0|^12.0"

use fab2s\Dt0\Dt0;
use fab2s\Dt0\Attribute\Rule;
use fab2s\Dt0\Attribute\Rules;
use fab2s\Dt0\Attribute\Validate;
use fab2s\Dt0\Validator\Validator;

#[Validate(Validator::class)]
#[Rules(
    email: new Rule('required|email'),
)]
class ContactDto extends Dt0
{
    public readonly string $email;

    #[Rule('required|string|min:2|max:100')]
    public readonly string $name;

    #[Rule('nullable|string|max:1000')]
    public readonly ?string $message;
}

// Throws ValidationException on failure
$contact = ContactDto::withValidation(
    email: 'test@example.com',
    name: 'John',
    message: 'Hello!',
);

Rules can be defined at three levels with clear priority: property #[Rule] > class #[Rules] > #[Validate] rules. The ValidatorInterface is open for custom implementations.

See Validation Documentation for locale configuration, custom translations, and custom validators.

Output

$dto->toArray();      // Array with objects intact, output casters applied
$dto->toJsonArray();  // Array with objects serialized (JsonSerializable)
$dto->toJson();       // JSON string
$dto->toGz();         // Gzipped JSON string
json_encode($dto);    // JSON (implements JsonSerializable)
(string) $dto;        // JSON (implements Stringable)

Output Filtering

// Exclude sensitive fields
$dto->without('password', 'apiKey')->toJson();

// Include only specific fields
$dto->only('id', 'name')->toArray();

// Add computed or protected properties
$dto->with('fullName', fn($d) => "$d->firstName $d->lastName")->toArray();
$dto->with('total', true)->toArray();       // calls getTotal()
$dto->with('internalField')->toArray();     // exposes protected property

Declarative output control with #[With] is also supported. See Output Documentation for details.

Immutable Operations

$copy = $dto->clone();
$updated = $dto->update(name: 'Jane', role: 'admin');
$dto->equals($updated);  // false

// Serialization round-trip
$restored = unserialize(serialize($dto));
$dto->equals($restored);  // true

Property Renaming

Map between external names (APIs, databases) and internal property names:

class ApiResponseDto extends Dt0
{
    #[Cast(renameFrom: 'created_at', renameTo: 'createdAtStr')]
    public readonly string $createdAt;

    // Accept multiple input names
    #[Cast(renameFrom: ['user_name', 'username', 'login'])]
    public readonly string $userName;
}

All renameTo values are automatically added to renameFrom, ensuring round-trip consistency.

Default Values

class ConfigDto extends Dt0
{
    #[Cast(default: 3600)]
    public readonly int $ttl;

    #[Cast(default: null)]
    public readonly ?string $prefix;

    #[Cast(default: true)]
    public readonly bool $enabled;
}

$config = ConfigDto::make();  // All defaults applied

Resolution order: provided value > Cast default > nullable default > promoted parameter default.

Attribute Inheritance

Dt0 resolves attributes up the parent class chain — both property-level and class-level:

class TimestampedDto extends Dt0
{
    #[Cast(in: DateTimeCaster::class, out: new DateTimeFormatCaster(DateTimeFormatCaster::ISO))]
    public readonly DateTimeImmutable $createdAt;
}

// Inherits Cast from TimestampedDto
class ArticleDto extends TimestampedDto
{
    public readonly string $title;
    public readonly DateTimeImmutable $createdAt;  // Redeclare for PHP < 8.4
}

$article = ArticleDto::make(title: 'Hello', createdAt: '2024-01-15');
$article->createdAt;  // DateTimeImmutable (inherited cast applied)

See Inheritance Documentation for multi-level inheritance, class attribute inheritance, and override patterns.

Performance

Reflection and attribute metadata compiled once per class, per process. Subsequent instantiations reuse cached data with zero reflection overhead.

Benchmarks

Dt0 vs spatie/laravel-data (PHP 8.5, 10,000 iterations)

Repeated serialization (same instance):

Output caching delivers ~107-292x improvements when serializing the same instance multiple times (API + logging, event sourcing, queue + monitoring, caching layers). Absolute timings are hardware-dependent; the speedup ratios are what matter.

php benchmark/compare-spatie.php

Extending

Dt0's attributes, casters, and validators are extensible. See Extending Documentation for interfaces, abstract classes, and compiled metadata access.

Exceptions

All exceptions extend ContextException with structured context for debugging:

Requirements

• PHP 8.2, 8.3, 8.4, or 8.5

Dependencies

• fab2s/context-exception - Contextual exceptions
• fab2s/enumerate - Enum utilities

Optional

• illuminate/validation + illuminate/translation - For standalone Validator
• nesbot/carbon - For CarbonCaster
• fab2s/math - For MathCaster

Contributing

Contributions are welcome. Please open issues and submit pull requests.

composer fix        # Code style (Laravel Pint)
composer test       # Run tests
composer cov        # Tests with coverage
composer stan       # PHPStan level 9 (src/)
composer stan-tests # PHPStan level 5 (tests/)

License

Dt0 is open-sourced software licensed under the MIT license.