A simplistic, flexible Data Transfer Object library written in PHP.

It's arguably a common practice to pass data as associative arrays between layers. For example, a service method to create a new user may look like this:

// UserService.php
public function createUser(array $attributes): User
{
    return User::create($attributes);
}

The method can be called by e.g., a controller this way:

// UserController.php
public function store(CreateUserRequest $request)
{
    $this->userService->create($request->toArray());
}

This kind of works, but with several drawbacks:

• An associative array is pretty much unstructured—there's virtually no restriction on what can be put in it or what the data type of each element should be. This makes the code hard to reason about (no exact clue what's inside the array) and can lead to serious security issues.
• One would always have to refer to the documentation (if one exists) for the "shape" of the array. This reduces both reusability and productivity.
• Static code analysis and IDE auto-completion support are greatly hindered.

Now imagine instead of using an arbitrary array, we use an object with typed properties:

// UserCreationData.php
class UserCreationData
{
    public string $email;
    public string $password;
    public ?int $age;
}

// UserService.php
public function createUser(UserCreationData $data): User
{
    return User::create($data->toArray());
}

// UserController.php
public function store(CreateUserRequest $request)
{
    $this->userService->create(UserCreationData::fromRequest($request));
}

With this approach, we have a clear idea of what fields to expect as user creation data, their types and other restrictions, and we can enjoy all type-hinting, auto-completion, static analysis etc. This is exactly what eve/dto allows you to do.

You can install eve/dto via Composer:

composer require eve/dto

This package requires PHP ≥7.4.

v1.x versions of this library include a strict type check—for example, assigning a string to a boolean property will throw an error. Though certainly useful, this feature doesn't belong in the scope of a DTO and has been removed from v2. You're encouraged to use a static analysis tool like PHPStan or Psalm for the task instead.

Following the example above, firstly, we make UserCreationData extends Eve\DTO\DataTransferObject and define all attributes as public properties:

class UserCreationData extends \Eve\DTO\DataTransferObject
{
    public string $email;
    public string $password;
    public ?int $age;
}

To construct a new UserCreationData instance, call make with an array of parameters:

$data = UserCreationData::make([
   'email' => '[email protected]',
   'password' => 'SoSecureWow',
   'age' => 30,
]);

Alternatively, you can explicitly set the attributes. The code above is essentially the same as:

$data = UserCreationData::make();
$data->email = '[email protected]';
$data->password = 'SoSecureWow';
$data->age = 30;

Or you can use the fluent set method, which can take either an associative array or two separated $name, $value parameters:

$data = UserCreationData::make()
    ->set('email', '[email protected]')
    ->set([
       'password' => 'SoSecureWow',
       'age' => 30,
    ]);

If any of the passed properties doesn't exist in the class definition, an exception will be thrown:

UserCreationData::make(['nope' => 'bar']); // throws "Public property $nope does not exist in class UserCreationData"

Then we can call the toArray() method to transform the object into an associative array:

$arr = $data->toArray(); // ['email' => '[email protected]', 'password' => 'SoSecureWow', 'age' => 30]

Note that non-set properties will NOT be included in the output array:

$data = UserCreationData::make();

// Only setting email now
$data->email = '[email protected]';

$arr = $data->toArray(); // ['email' => '[email protected]']

This is especially handy e.g., if you have a method to patch a database record, as it allows the operation to be totally flexible—you can patch all properties or only a subset of them.

Nested DTOs will be transformed into their corresponding arrays:

class UserCreationData extends \Eve\DTO\DataTransferObject
{
    public string $email;
    public string $password;
    public UserInformationData $information;
}

class UserInformationData extends \Eve\DTO\DataTransferObject
{
    public int $age;
}

$data = UserCreationData::make([
   'email' => '[email protected]',
   'password' => 'SoSecureWow',
   'information' => UserInformationData::make(['age' => 30]),
]);

$data->toArray(); // ['email' => '[email protected]', 'password' => 'SoSecureWow', ['information' => ['age' => 30]]

• DataTransferObject::only(string ...$names): static returns the object that includes only $names in the output array.

  $data = UserCreationData::make([
     'email' => '[email protected]',
     'password' => 'SoSecureWow',
     'age' => 30,
  ]);
  
  $data->only('email', 'password')->toArray(); // ['email' => '[email protected]', 'password' => 'SoSecureWow']

• DataTransferObject::except(string ...$names): static returns the object that exludes $names from the output array.

  $data = UserCreationData::make([
     'email' => '[email protected]',
     'password' => 'SoSecureWow',
     'age' => 30,
  ]);
  
  $data->except('email', 'password')->toArray(); // ['age' => 30]

• DataTransferObject::compact(): static returns the object that includes only properties whose values are not NULL in the output array.

  $data = UserCreationData::make([
     'email' => '[email protected]',
     'password' => 'SoSecureWow',
     'age' => null,
  ]);
  
  $data->compact()->toArray(); // ['email' => '[email protected]', 'password' => 'SoSecureWow']

• DataTransferObject::get(string $name, $default = null): mixed returns the value of $name property. If $name doesn't exist in the class definition, an exception will be thrown. If $name exists but not initialized, $default will be returned.

  Important: PHP treats non-typed properties e.g., public $prop as initialized with NULL.

  $data = UserCreationData::make([
     'email' => '[email protected]',
     'password' => 'SoSecureWow',
  ]);
  
  $data->get('email'); // '[email protected]'
  $data->password; // 'SoSecureWow'
  
  $data->age; // throws "UserCreationData::$age must not be accessed before initialization."
  $data->get('age', 30); // 30
  
  $data->get('nope'); // throws "Public property $nope does not exist in class UserCreationData."
  $data->nope; // throws "Public property $nope does not exist in class UserCreationData."

Though eve/dto is inspired by and shares some similarities with spatie/data-transfer-object, the two packages have certain differences, the most significant of which are as follows:

• spatie/data-transfer-object requires all not-null properties to be supplied right from instantiation. This behavior is not always feasible or desirable (refer to the data patching example above). eve/dto opts for a much more forgiving approach, which allows a DTO to be created with any subset of properties.
• spatie/data-transfer-object can't detect or prevent you from assigning a non-existent property directly (e.g., $userData->non_existent = 'foo'), which is something eve/dto does to help ensure your object's integrity.
• spatie/data-transfer-object implements such features as "Data Transfer Object Collection" and "Flexible Data Transfer Objects." To keep things simple and concise, eve/dto doesn't have these implementations.

MIT