<?php
class Foo {
    function __construct (&$arr) {
        $this->arr = &$arr;
    }
    function createInstance () {
        $reflectionClass = new ReflectionClass("Bar");

        return $reflectionClass->newInstanceArgs(array($this, $this->arr));
    }
    function mod($key, $val) {
        $this->arr[$key] = $val;
    }
}

class Bar {
    function __construct (&$foo, &$arr) {
        $this->foo = &$foo;
        $this->arr = &$arr;
    }
    function mod($key, $val) {
        $this->arr[$key] = $val;
    }
}

$arr = array();

$foo = new Foo($arr);

$arr["x"] = 1;

$foo->mod("y", 2);

$bar = $foo->createInstance();

$bar->mod("z", 3);

echo "<pre>";
print_r($arr);
print_r($foo);
print_r($bar);
echo "</pre>";
?>