Description:
------------
If offsetGet() returns by-ref it should not be possible to assign to it by-ref.

It does not even emit "Notice: Indirect modification of overloaded element of ArrayAccessImpl has no effect".

It just silently does nothing.

Test script:
---------------
<?php
// essentially tests/classes/array_access_012.phpt, with offsetGet returning by-ref

class ArrayAccessImpl implements ArrayAccess {
        private $data = array();

        public function offsetUnset($index) {}

        public function offsetSet($index, $value) {
                $this->data[$index] = $value;
        }

        public function &offsetGet($index) {
                return $this->data[$index];
        }

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

$data = new ArrayAccessImpl();
$test = 'some data';
$data['element'] = NULL; // prevent notice
$data['element'] = &$test;
var_dump($data['element']);

Expected result:
----------------
Fatal error: Uncaught Error: Cannot assign by reference to overloaded object ...

Actual result:
--------------
NULL