Classes

classes.php

<?php

abstract class LifeForm
{
    protected $firstName;
    protected $middleName;
    protected $lastName;

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

    public function getFirstName(): string
    {
        return $this->firstName;
    }

    public function getMiddleName(): string
    {
        return $this->middleName;
    }

    public function getLastName(): string
    {
        return $this->lastName;
    }

}

class Person extends LifeForm
{
    public function __construct(string $firstName,  string $lastName, string $middleName = "")
    {
        parent::__construct($firstName, $lastName, $middleName);
    }

}

class Employee extends Person
{
    protected $id;

    public function __construct(int $id, string $firstName,  string $lastName, string $middleName = "")
    {
        $this->id = $id;
        parent::__construct($firstName, $lastName, $middleName);
    }

    public function getId(): int
    {
        return $this->id;
    }

}

class Pet extends LifeForm
{
    public function __construct(string $firstName,  string $lastName="", string $middleName = "")
    {
        parent::__construct($firstName, $lastName, $middleName);
    }
}

// Quick and dirty tests to ensure it works properly

$pet1 = new Pet('Fluffy', 'Nutter', 'Mac');
echo $pet1->getFirstName() . ' ' . $pet1->getMiddleName() . ' ' . $pet1->getLastName();

echo PHP_EOL;

$pet2 = new Pet('Zinga', 'Ray');
echo $pet2->getFirstName() . ' ' . $pet2->getMiddleName() . ' ' . $pet2->getLastName();

echo PHP_EOL;

$pet3 = new Pet('Spot');
echo $pet3->getFirstName() . ' ' . $pet3->getMiddleName() . ' ' . $pet3->getLastName();

echo PHP_EOL;

$person1 = new Person('Joe', 'Smith');
echo $person1->getFirstName() . ' ' . $person1->getLastName();

echo PHP_EOL;

$person2 = new Person('Martha', 'Redhouse', 'Lee');
echo $person2->getFirstName() . ' ' . $person2->getMiddleName() . ' ' . $person2->getLastName();

echo PHP_EOL;

$employee1 = new Employee(362, 'Bob', 'Williams', 'Howard');
echo "({$employee1->getId()}) " . $employee1->getFirstName() . ' ' . $employee1->getMiddleName() . ' ' . $employee1->getLastName();

echo PHP_EOL;

$employee2 = new Employee(496, 'Lucy', 'Lou');
echo "({$employee2->getId()}) " . $employee2->getFirstName() . ' ' . $employee2->getLastName();

Thanks for the example.