reference_array.php

<?php
class Hoge {
    public $foo;
    public function __construct(&$foo) {
        $this->foo =& $foo;
    }
    public function &get_foo() {
        return $this->foo['bar'];
    }
    public function aaa() {
        $bar_foo =& $this->get_foo();
        $bar_foo['num'] = 10000;
    }
}

$foo = array('bar' => array('num' => 23));
$hoge = new Hoge($foo);

print_r($foo);
$hoge->aaa();
print_r($foo);

//Array
//(
//    [bar] => Array
//        (
//            [num] => 23
//        )
//
//)
//Array
//(
//    [bar] => Array
//        (
//            [num] => 10000
//        )
//)