Description:
------------
That code works:

class A{
	private $data;

	public function __construct() {
		$this->data = new stdClass();
	}

	public function & __get($property) {
		if (isset($this->data->$property)) {
			return $this->data->$property;
		}
		return null;
	}

	public function __set($property,$value) {
		$this->data->$property = $value;
	}
}

function chgTxt(& $txt) {
	$txt = '-----';
}

$o = new A();

$o->int = 1;
$o->int++;
echo $o->int,'<br />';//result: 2 - reference in A::get() works fine

$o->txt = 'string';
chgTxt($o->txt);
echo $o->txt,'<br />';//result: '----' - reference works

Reproduce code:
---------------
That code doesn't work:

class A{
	private $data;

	public function __construct() {
		$this->data = new stdClass();
	}

	public function & __get($property) {
		return isset($this->data->$property) ? $this->data->$property : null;
	}

	public function __set($property,$value) {
		$this->data->$property = $value;
	}
}

function chgTxt(& $txt) {
	$txt = '-----';
}

$o = new A();

$o->int = 1;
$o->int++;
echo $o->int,'<br />';//result: 2 - reference in A::get() works fine

$o->txt = 'string';
chgTxt($o->txt);
echo $o->txt,'<br />';//result: 'string' - reference doesn't work

Expected result:
----------------
2
----

Actual result:
--------------
2
string