Laravel DTOs

Laravel DTOs

Never pass multiple primitive values. Always wrap data in Data objects.

Related guides:

• dto-transformers.md - Transform external data into DTOs
• test-factories.md - Create hydrated DTOs for tests

Philosophy

DTOs provide:

• Type safety and IDE autocomplete
• Clear contracts between layers
• Test factories for easy test data generation
• Validation integration
• Transformation from requests to domain objects

Spatie Laravel Data Package

Uses Spatie Laravel Data. Refer to official docs for package features. This guide covers project-specific patterns and preferences.

Use ::from() with Arrays

Always prefer ::from() with arrays where keys match constructor property names. Let the package handle casting based on property types.

// ✅ PREFERRED - Let package cast automatically
$data = CreateOrderData::from([
    'customerEmail' => $request->input('customer_email'),
    'deliveryDate' => $request->input('delivery_date'),  // String → CarbonImmutable
    'status' => $request->input('status'),               // String → OrderStatus enum
    'items' => $request->collect('items'),               // Array → Collection<OrderItemData>
]);

// ❌ AVOID - Manual casting in calling code
$data = new CreateOrderData(
    customerEmail: $request->input('customer_email'),
    deliveryDate: CarbonImmutable::parse($request->input('delivery_date')),
    status: OrderStatus::from($request->input('status')),
    items: OrderItemData::collect($request->input('items')),
);

Why prefer ::from():

• Package handles type casting automatically based on constructor property types
• Cleaner calling code without manual casting
• Consistent transformation behavior
• Leverages the full power of the package

When new is acceptable:

• In test factories where you control all values
• When values are already the correct type
• In formatters inside the DTO constructor

Avoid Case Mapper Attributes

Don't use #[MapInputName] or case mapper attributes. Map field names explicitly in calling code.

// ❌ AVOID - Case mapper attributes on the class
#[MapInputName(SnakeCaseMapper::class)]
class CreateOrderData extends Data
{
    public function __construct(
        public string $customerEmail,    // Auto-maps from 'customer_email'
    ) {}
}

// ✅ PREFERRED - Explicit mapping in calling code
CreateOrderData::from([
    'customerEmail' => $request->input('customer_email'),
]);

Why avoid case mappers:

• Explicit mapping is clearer and more maintainable
• Different API versions may have different field names
• Transformers provide a single place to see all mappings
• Avoids magic behavior that's hard to trace

Date Casting is Automatic

The package automatically casts date strings to Carbon or CarbonImmutable based on property types. Configure the expected date format in the package config.

// config/​data.php
return [
    'date_format' => 'Y-m-d H:i:s',  // Or ISO 8601: 'Y-m-d\TH:i:s.u\Z'
];

class OrderData extends Data
{
    public function __construct(
        public CarbonImmutable $createdAt,   // Automatically cast from string
        public ?CarbonImmutable $shippedAt,  // Nullable dates work too
    ) {}
}

// ✅ Just pass the string - package handles casting
$data = OrderData::from([
    'createdAt' => '2024-01-15 10:30:00',
    'shippedAt' => null,
]);

Basic Structure

<?php

declare(strict_types=1);

namespace App\Data;

use App\Enums\OrderStatus;
use Carbon\CarbonImmutable;
use Illuminate\Support\Collection;

/​**
 * @see \Database\Factories\Data\CreateOrderDataFactory
 */
class CreateOrderData extends Data
{
    public function __construct(
        public string $customerEmail,
        public ?string $notes,
        public ?CarbonImmutable $deliveryDate,
        public OrderStatus $status,
        /​** @var Collection<int, OrderItemData> */
        public Collection $items,
        public ShippingAddressData $shippingAddress,
        public BillingAddressData $billingAddress,
    ) {
        // Apply formatters in constructor
        $this->customerEmail = EmailFormatter::format($this->customerEmail);
    }
}

Key Patterns

Constructor Property Promotion

Always use promoted properties:

public function __construct(
    public string $name,
    public ?string $description,
    public bool $active = true,
) {}

Not:

public string $name;
public ?string $description;

public function __construct(string $name, ?string $description)
{
    $this->name = $name;
    $this->description = $description;
}

Type Everything

public string $email;                          // Required string
public ?string $phone;                         // Nullable string
public CarbonImmutable $createdAt;             // DateTime (immutable)
public OrderStatus $status;                    // Enum
public Collection $items;                      // Collection
public AddressData $address;                   // Nested DTO

Collections with PHPDoc

/​** @var int[] */
public array $productIds;

/​** @var Collection<int, OrderItemData> */
public Collection $items;

Nested Data Objects

class OrderData extends Data
{
    public function __construct(
        public CustomerData $customer,
        public ShippingAddressData $shipping,
        public BillingAddressData $billing,
        /​** @var Collection<int, OrderItemData> */
        public Collection $items,
    ) {}
}

Formatters

Apply formatting in the constructor:

public function __construct(
    public string $email,
    public ?string $phone,
    public ?string $postcode,
) {
    $this->email = EmailFormatter::format($this->email);
    $this->phone = $this->phone ? PhoneFormatter::format($this->phone) : null;
    $this->postcode = $this->postcode ? PostcodeFormatter::format($this->postcode) : null;
}

Example formatter (app/​Data/​Formatters/​EmailFormatter.php):

<?php

declare(strict_types=1);

namespace App\Data\Formatters;

class EmailFormatter
{
    public static function format(string $email): string
    {
        return strtolower(trim($email));
    }
}

Static Factory Methods on DTOs

For smaller applications or when starting out, add static from* methods directly on the DTO class. This provides factory-like behavior before complexity warrants separate transformers.

Method naming: from{SourceType} - e.g., fromArray, fromRequest, fromModel

class OrderData extends Data
{
    public function __construct(
        public string $customerEmail,
        public ?string $notes,
        public OrderStatus $status,
        /​** @var Collection<int, OrderItemData> */
        public Collection $items,
    ) {}

    public static function fromRequest(CreateOrderRequest $request): self
    {
        return self::from([
            'customerEmail' => $request->input('customer_email'),
            'notes' => $request->input('notes'),
            'status' => $request->input('status'),
            'items' => $request->input('items'),
        ]);
    }

    public static function fromModel(Order $order): self
    {
        return self::from([
            'customerEmail' => $order->customer_email,
            'notes' => $order->notes,
            'status' => $order->status,
            'items' => $order->items->toArray(),
        ]);
    }
}

When to use static methods on DTO:

• Smaller applications with fewer DTOs
• Simple transformations that don't need dedicated testing
• When mapping is tightly coupled to a single DTO

When to use separate transformers:

• Multiple external sources map to the same DTO
• Complex transformation logic requiring extensive testing
• Larger applications with clear separation of concerns

Model Casts

Cast model JSON columns to DTOs:

class Order extends Model
{
    protected function casts(): array
    {
        return [
            'metadata' => OrderMetadataData::class,
            'status' => OrderStatus::class,
        ];
    }
}

Usage:

// Store
$order = Order::create([
    'metadata' => $metadataData,  // OrderMetadataData instance
]);

// Retrieve
$metadata = $order->metadata;  // Returns OrderMetadataData instance

Naming Conventions

Directory Structure

app/​Data/
├── CreateOrderData.php
├── UpdateOrderData.php
├── OrderData.php
├── Concerns/
│   └── HasTestFactory.php
├── Formatters/
│   ├── EmailFormatter.php
│   ├── PhoneFormatter.php
│   └── PostcodeFormatter.php
└── Transformers/
    ├── PaymentDataTransformer.php
    ├── Web/
    │   └── OrderDataTransformer.php
    └── Api/
        └── V1/
            └── OrderDataTransformer.php

Usage in Controllers

Controllers transform requests to DTOs via transformers:

<?php

declare(strict_types=1);

namespace App\Http\Web\Controllers;

use App\Actions\Order\CreateOrderAction;
use App\Data\Transformers\Web\OrderDataTransformer;
use App\Http\Web\Requests\CreateOrderRequest;
use App\Http\Web\Resources\OrderResource;

class OrderController extends Controller
{
    public function store(
        CreateOrderRequest $request,
        CreateOrderAction $action
    ): OrderResource {
        $order = $action(
            user(),
            OrderDataTransformer::fromRequest($request)
        );

        return OrderResource::make($order);
    }
}

Usage in Actions

Actions accept DTOs as parameters:

class CreateOrderAction
{
    public function __invoke(User $user, CreateOrderData $data): Order
    {
        return DB::transaction(function () use ($user, $data) {
            return $user->orders()->create([
                'customer_email' => $data->customerEmail,
                'notes' => $data->notes,
                'status' => $data->status,
            ]);
        });
    }
}

Transformers

For complex transformations (external APIs, webhooks, field mappings), use dedicated transformer classes.

→ Complete guide: dto-transformers.md

// External system data
$data = PaymentDataTransformer::fromStripePaymentIntent($webhook['data']);

// Request with version-specific field names
$data = OrderDataTransformer::fromRequest($request);

Hierarchy of preference:

1. Data::from($array) - Simple cases, direct mapping
2. Data::fromRequest() - Static method on DTO for smaller apps
3. Transformer::from*() - Complex transformations, multiple sources

Test Factories

Create hydrated DTOs for tests using the HasTestFactory trait.

→ Complete guide: test-factories.md

Link DTOs to factories with PHPDoc:

/​**
 * @see \Database\Factories\Data\CreateOrderDataFactory
 * @method static CreateOrderDataFactory testFactory()
 */
class CreateOrderData extends Data
{
    // ...
}

Usage:

$data = CreateOrderData::testFactory()->make();
$collection = OrderItemData::testFactory()->collect(count: 5);

// With overrides
$data = CreateOrderData::testFactory()->make([
    'customerEmail' => '[email protected]',
]);

Testing DTOs

use App\Data\CreateOrderData;

it('can create DTO from array', function () {
    $data = CreateOrderData::from([
        'customerEmail' => '[email protected]',
        'notes' => 'Test notes',
        'status' => 'pending',
    ]);

    expect($data)
        ->customerEmail->toBe('[email protected]')
        ->notes->toBe('Test notes');
});

it('formats email in constructor', function () {
    $data = new CreateOrderData(
        customerEmail: '  [email protected]  ',
        notes: null,
        status: OrderStatus::Pending,
    );

    expect($data->customerEmail)->toBe('[email protected]');
});