accessing an object like an array

I am hoping someone can point me in the right direction.

I have an object that at some point sets one of it's variables as an array.

class myClass
{
  private $data = array()

  public function __construct($newData=array())
  {
    $this->setData($newData);
  }

  public function getData()
  {
    return $this->data;
  }

  public function setData($newData=array())
  {
    $this->data = $newData;
  }
}

$dataObj = new myClass($someDataArray);

// I want to be able to do.

print $dataObh['myArrayKey']

// and get back the data that that key holds in the object $data variable

I know it can be done, I just don't know the specifics, and I think it has something to do with Obect Iteration, but the docs are confusing me. Thanks.