Optional parameters on request class - php

Question

What is the proper way to handle optional parameters on a service request?
Lets say in this scenario i want to have also $title as optional parameter
<?php
namespace Lw\Application\Service\Wish;
class AddWishRequest
{
private $userId;
private $email;
private $content;
public function __construct($userId, $email, $content)
{
$this->userId = $userId;
$this->email = $email;
$this->content = $content;
}
public function userId()
{
return $this->userId;
}
public function email()
{
return $this->email;
}
public function content()
{
return $this->content;
}
}
Example from here

Answer 1

Usually in DDD and following the rules of clean code also, if you have optional parameters, you have multiple constructors, two in this case:
One for just the mandatory arguments.
One for all the arguments including the optional but in this constructor it would be mandatory too.
If you wanna construct the object without the optional argument you call the first one. And if you wanna supply a non null optional argument you use the second one.
Usually you should use factory methods with meaningful names, and hide the constructors.
AddWishRequest.create ( userId, email, content)
AddWishRequest.createWithTitle ( userId, email, content, title )

Answer 2

You can use optional arguments in any function call, also the constructor. Best practice is, to preceed "get" to the getters.
public function __construct($userId, $email, $content, $title = "")
means, $title is an optional argument. When not supplied, it is set to an empty string. You also could provide any other type or value.
namespace Lw\Application\Service\Wish;
class AddWishRequest
{
private $userId;
private $email;
private $content;
private $title;
public function __construct($userId, $email, $content, $title = "")
{
$this->userId = $userId;
$this->email = $email;
$this->content = $content;
$this->title = $title;
}
public function getUserId()
{
return $this->userId;
}
public function getEmail()
{
return $this->email;
}
public function getContent()
{
return $this->content;
}
public function getTitle()
{
return $this->title;
}
}
Update
If you just declare a property like
private $property
then accessing it via $this->property with always be null (until you set a value). You should make the getter responsible for returning the correct values.
Following example will always return an array making use of the NULL-coalesce operator:
if $something is true (or has an array content) will return $something
else will return empty array
public function getSomething() : array {
return $this->something ?? [];
}