An abstract DTO class I've been experimenting with recently.

AbstractDTO.php

<?php

namespace App\DTO;

use Illuminate\Support\Str;
use Illuminate\Contracts\Support\Jsonable;
use Illuminate\Contracts\Support\Arrayable;

/**
 * An abstract class to provide out of the box functionality for DTO objects.
 *
 * DTOs use camel case properties, as they look nicer.
 * This class returns properties in arrays or json as snake case (to match DB fields)
 *
 */
abstract class AbstractDTO implements Jsonable, Arrayable
{
    public function __construct(array $data = [])
    {
        foreach ($data as $key => $datum) {
            $this->set($key, $datum);
        }
    }

    public function toArray()
    {
        $ar = [];
        foreach ($this->getProperties() as $key) {
            if (isset($this->$key)) {
                $ar[Str::snake($key)] = $this->get($key);
            }
        }
        return $ar;
    }

    public function toJson($options = 0)
    {
        return json_encode($this->toArray(), $options);
    }

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

    public function get($name)
    {
        $property = Str::camel($name);
        if (property_exists($this, $property)) {
            return $this->{$property};
        }

        throw new \Exception('Property ' . $property . ' does not exist on ' . get_class($this));
    }

    public function __set($name, $value)
    {
        return $this->set($name, $value);
    }

    public function set($name, $value)
    {
        $property = Str::camel($name);
        if (!property_exists($this, $property)) {
            throw new \Exception('Can\'t set property ' . $property . ' that does not exist on ' . get_class($this));
        }
        $this->{$property} = $value;
    }

    private function getProperties()
    {
        return array_keys(get_object_vars($this));
    }
}

ExampleDTO.php

<?php

namespace App\DTO;

class Client extends AbstractDTO
{
    public $name;

    public $slug;

    public $notes = '';

    public $isActive = true;
}