ObjectDesingStyleGuide.php

<?php
//Not meant to be extended from.
final class Service
{
  //All properties are immutable

  private $properties;

  //All arguments are required. Don’t inject contextual information; make the service reusable. Dependencies are actual dependencies, not service locators.
  public function __construct($dependencies, $configurationValues)
  {
    // Only assign arguments to properties.
  }
  public function commandMethod($input, $context): void
  {
    // Pass data relevant to the job, plus contextual information (current time, current user, etc.). Validate input arguments. Perform the task. Produce side effects.
  }
  public function queryMethod($input, $context): returnType
  {
    //Validate input arguments. Produce no   side effects, only return information.
  }
}

//Not meant to be extended from.

final class Entity
{
  //Properties can be mutable.
  private $properties;
  private array $events = [];
  private function __construct()
  {
  }
  //  Use named constructors as meaningful ways of instantiating the object. 
  public static function namedConstructor($values)
  {
    //Validate arguments. Instantiate a new copy. Assign arguments to properties. Record domain event(s).
  }

  //Pass data relevant to the job, plus contextual information (current time, current user, etc.).
  public function commandMethod($input, $context): void
  {
    //  Validate input arguments. Validate state transitions. Record domain events.
  }
  // Limit the number of query methods exposing state
  public function queryMethod(): returnType
  {
    // ...
  }
  public function releaseEvents(): array
  {
    // Return recorded domain events.

  }
}

//Not meant to be extended from.
final class ValueObject
{
  //All properties are immutable.
  private $properties;
  private function __construct()
  {
  }

  //Named constructors as meaningful ways of instantiating the object.
  public static function namedConstructor($values)
  {
    // Validate arguments. Instantiate a new copy. Assign arguments to properties. Record domain event(s).
  }
  // Use declarative names for  modifiers (e.g. with…())
  public function modifier($input): ValueObject
  {
    //Return a modified copy of the original.

  }
  // Limit the number of query methods
  public function queryMethod(): returnType
  {
    // ...
  }
}