gistfile1.php

<?php

class A {
	protected $_properties = [
		'a' => 1,
		'b' => 2
	];
	
	public function &get($property)
	{
		if (!strlen((string)$property)) {
			throw new InvalidArgumentException('Cannot get an empty property');
		}

		$value = null;
		$method = '_get' . ucfirst($property);

		if (isset($this->_properties[$property])) {
			$value =& $this->_properties[$property];
		}

		if (is_callable([$this, $method])) {
			$result = $this->{$method}($value);
			return $result;
		}
		return $value;
	}
	
	public function &__get($property)
	{
		return $this->get($property);
	}
				
	public function _getFoo() {
		return $this->_properties['b'];
	}
}

$a = new A;
$array = [$a];
foreach ($array as &$value) {
	var_dump($value->a);
	unset($value->a);
	var_dump($value->a);	
	var_dump($value->get('foo'));
	unset($value->foo);
	var_dump($value->get('foo'));
}