class HardDiskDrive {

  public $brand;
  public $color;
  public $cpu;
  public $workState;

  protected $memory;
  protected $hardDisk;

  private $price;

  public function __construct($brand, $color, $cpu, $workState, $memory, $hardDisk, $price) {

    $this->brand = $brand;
    $this->color = $color;
    $this->cpu  = $cpu;
    $this->workState = $workState;
    $this->memory = $memory;
    $this->hardDisk = $hardDisk;
    $this->price = $price;
  }

}

$hardDiskDrive = new HardDiskDrive('希捷', 'silver', 'tencent', 'well', '1T', 'hard', '$456');

foreach ($hardDiskDrive as $property => $value) {

  var_dump($property, $value);
  echo '<br>';
}

class Team implements Iterator {

  //private $name = 'itbsl';
  //private $age = 25;
  //private $hobby = 'fishing';

  private $info = ['itbsl', 25, 'fishing'];

  public function rewind()
  {
    reset($this->info); //重置数组指针
  }

  public function valid()
  {
    //如果为null,表示没有元素，返回false
    //如果不为null,返回true

    return !is_null(key($this->info));
  }

  public function current()
  {
    return current($this->info);
  }

  public function key()
  {
    return key($this->info);
  }

  public function next()
  {
    return next($this->info);
  }

}

$team = new Team();

foreach ($team as $property => $value) {

  var_dump($property, $value);
  echo '<br>';
}