Description:
------------
Overloaded properties implement $x->y++ by calling __set('y', __get('y') + 1). 

The same does not work for ArrayAccess. ArrayAccess only supports $x[0]++ if offsetGet() returns by reference, in which case the increment is performed on the reference.

This is inconsistent both with the overloaded property behavior and with compound assignment operations on ArrayAccess. That is, $x[0] += 1 *does* work with a by-value offsetGet().

Test script:
---------------
<?php

class Test implements ArrayAccess {
    public function __get($k) {
        return 1;
    }
    public function __set($k, $v) {
        echo "__set($v)\n";
    }
    
    public function offsetGet($k) {
        return 1;
    }
    public function offsetSet($k, $v) {
        echo "offsetSet($v)\n";
    }
    public function offsetExists($k) {}
    public function offsetUnset($k) {}
}

$t = new Test;
echo "Property:\n";
$t->x++;
echo "Offset:\n";
$t[0]++;

Expected result:
----------------
Property:
__set(2)
Offset:
offsetSet(2)

Actual result:
--------------
Property:
__set(2)
Offset:
Notice: Indirect modification of overloaded element of Test has no effect