json serializable class

json_serializable.php

<?php

/**
 * Class Person
 */
class Person implements JsonSerializable
{
    /**
     * @var string
     */
    private $firstname;

    /**
     * @var string
     */
    private $lastname;

    /**
     * @return string
     */
    public function getFirstname(): string
    {
        return $this->firstname;
    }

    /**
     * @param string $firstname
     * @return Person
     */
    public function setFirstname(string $firstname): Person
    {
        $this->firstname = $firstname;
        return $this;
    }

    /**
     * @return string
     */
    public function getLastname(): string
    {
        return $this->lastname;
    }

    /**
     * @param string $lastname
     * @return Person
     */
    public function setLastname(string $lastname): Person
    {
        $this->lastname = $lastname;
        return $this;
    }

    /**
     * @return array|mixed
     */
    public function jsonSerialize()
    {
        return [
            'person' => [
                'firstname' => $this->firstname,
                'lastname' => $this->lastname
            ]
        ];
    }
}

$person = new Person();
$person
    ->setFirstname('Jeff')
    ->setLastname('Johnson');

echo json_encode($person);