An example of how one might implement a pseudo-friend relationship between two PHP objects.

php-friend.php

<?php

class SampleEntity
{
    private $friend = 'SampleEntityPresenter';

    protected $firstName;
    protected $lastName;

    public function __construct($firstName, $lastName)
    {
        $this->firstName = $firstName;
        $this->lastName = $lastName;
    }

    public function __get($property)
    {
        if ($this->friend !== $this->getCallingClass()) {
            throw new Exception("SampleEntity can only be accessed by SampleEntityPresenter.");
        }

        return $this->$property;
    }

    private function getCallingClass()
    {
        $backtrace = debug_backtrace(DEBUG_BACKTRACE_PROVIDE_OBJECT);
        $backtrace = end($backtrace);
        return $backtrace['class'];
    }
}

class SampleEntityPresenter
{
    private $entity;

    public function __construct(SampleEntity $entity)
    {
        $this->entity = $entity;
    }

    public function getFullName()
    {
        return $this->entity->firstName . ' ' . $this->entity->lastName;
    }
}

// Sample code.
$entity = new SampleEntity('Dustin', 'Wheeler');
$presenter = new SampleEntityPresenter($entity);

// Access through presenter succeeds.
echo $presenter->getFullName() . PHP_EOL;

// Direct-access fails with Exception.
echo $entity->firstName . ' ' . $entity->lastName . PHP_EOL;