Data Transfer Objects (DTO)

A Data Transfer Object (DTO) is a simple object used to pass data between different layers of your application, such as from a Controller to a Repository. DTOs ensure that the data being passed is structured, type-safe, and validated, preventing the “array of mystery” anti-pattern in your WordPress plugin.

WpMVC provides a powerful Base DTO class that uses PHP Reflection to automate the conversion of objects into associative arrays. This is particularly useful for database operations where you need a clean, structured array of values.

Key Features

Automatic Serialization: Converts camelCase or snake_case properties into arrays via to_array().
Initialization Awareness: Only includes properties that have been explicitly initialized.
Selective Exclusion: Easily exclude specific properties (like id) from being included in database payloads.
Recursive Support: Automatically converts nested DTOs or arrays of DTOs into arrays.

Defining a DTO

To create a DTO, extend the base WpMVC\DTO\DTO class. By convention, DTOs should be placed in the app/DTO directory.

Generating DTOs

Use the make:dto Artisan command to generate a new DTO class:


php artisan make:dto PostDTO

Define your properties and their corresponding getters and setters:


<?php
 
namespace MyPluginNamespace\App\DTO;
 
defined( 'ABSPATH' ) || exit;
 
use MyPluginNamespace\WpMVC\DTO\DTO;
 
class PostDTO extends DTO
{
    protected int $id;
    protected string $title;
    protected string $content;
    protected bool $is_published;
 
    public function set_id( int $id ): self
    {
        $this->id = $id;
        return $this;
    }
 
    public function get_id(): int
    {
        return $this->id;
    }
 
    public function set_title( string $title ): self
    {
        $this->title = $title;
        return $this;
    }
 
    public function get_title(): string
    {
        return $this->title;
    }
 
    // Boolean specific getter: is_{property_name}
    public function is_is_published(): bool
    {
        return $this->is_published;
    }
}

Naming Convention: The to_array() method expects getters to follow the get_{property_name} pattern, and booleans to follow the is_{property_name} pattern.

Filtering and Serialization

Handling Uninitialized Properties

The to_array() method is intelligent. If you haven’t set a value for a property (e.g., $content), it will be skipped entirely in the resulting array. This is ideal for PATCH requests where you only want to update a subset of columns.

Excluding Properties

By default, the id property is excluded from the to_array() output to prevent accidentally overwriting primary keys during database updates. You can customize this list using $exclude_to_array or the set_exclude_to_array() method.


<?php
 
namespace MyPluginNamespace\App\DTO;
 
defined( 'ABSPATH' ) || exit;
 
use MyPluginNamespace\WpMVC\DTO\DTO;
 
class UserDTO extends DTO
{
    protected array $exclude_to_array = [ 'id', 'password', 'internal_meta' ];
}

Recursive DTOs

If your DTO contains other DTOs (either as a single property or an array of objects), to_array() will recursively convert them.

app/DTO/OrderDTO.php


class OrderDTO extends DTO {
    protected array $items; // An array of ItemDTO objects
 
    public function get_items(): array {
        return $this->items;
    }
}
 
// Result of $orderDto->to_array():
// [
//    'items' => [
//        ['name' => 'Pizza', 'price' => 10],
//        ['name' => 'Soda', 'price' => 2]
//    ]
// ]

Usage Patterns

DTOs are typically used to bridge the gap between a Request and a Repository, providing a clean contract between layers.

In a Controller


<?php
 
namespace MyPluginNamespace\App\Http\Controllers;
 
defined( 'ABSPATH' ) || exit;
 
use MyPluginNamespace\App\DTO\PostDTO;
use MyPluginNamespace\App\Repositories\PostRepository;
 
class PostController extends Controller
{
    public function store( $request, PostRepository $repo )
    {
        $dto = ( new PostDTO() )
            ->set_title( $request['title'] )
            ->set_content( $request['content'] );
 
        $repo->create( $dto );
    }
}

In a Repository


<?php
 
namespace MyPluginNamespace\App\Repositories;
 
defined( 'ABSPATH' ) || exit;
 
use MyPluginNamespace\WpMVC\DTO\DTO;
use MyPluginNamespace\WpMVC\Database\Query\Builder;
 
class PostRepository extends Repository
{
    public function create( DTO $dto )
    {
        // to_array() returns only the initialized properties
        return $this->get_query_builder()->insert_get_id( $dto->to_array() );
    }
}