utilidade para classes no.php

<?php

class Users implements JsonSerializable{
  private $_data = array();
  public function addUser(User $user){
    $this->_data[] = $user;
  }
  public function jsonSerialize(){
    return $this->_data;
  }

  public function __toString(){
    return json_encode($this->jsonSerialize());
  }
}

class User implements JsonSerializable {
  private $_name = null;
  public function getName(){
    return $this->_name;
  }
  public function setName($value){
    $this->_name = $value;
  }

  public function jsonSerialize(){
    return [
      "name" => $this->_name
    ];
  }
}

$users = new Users();
$user = new User();
$user->setName('Carinha dahora');
$users->addUser($user);

echo $users;