<?php

class foo {
    public $value = 1;

    public function &getValue() {
        return $this->value;
    }
}

// 1
$obj = new foo;
$myValue = &$obj->getValue(); // $myValue is a reference to $obj->value, which is 1.

$obj->value = 2;
echo $myValue; // 2

// 2
$obj = new foo;
$myValue = &$obj->getValue(); // $myValue is a reference to $obj->value, which is 1.

$myValue = 3;
echo $obj->value; // 3