gistfile1.txt

class TArrayAccess implements \ArrayAccess
{
    private $arr;

    public function offsetExists($offset)
    {
        return isset($this->arr[$offset]);
    }

    public function offsetGet($offset)
    {
        return $this->arr[$offset];
    }

    public function offsetSet($offset, $value)
    {
        $this->arr[$offset] = &$value;
    }

    public function offsetUnset($offset)
    {
        unset($this->arr[$offset]);
    }
}

$a = new TArrayAccess();
$b = 10;
$a['a'] = $b;
$b = 20;

var_dump($a['a']);