test.php

<?php
class Cache {
        protected $cache = array();

        function set($value)
        {
                if (is_object($value))
                       $this->cache = clone $value;

                $this->cache = $value;
        }

        function get()
        {
                if (is_object($this->cache))
                        return clone $this->cache;

                return $this->cache;
        }
}

$cache = new Cache;

$a = new stdClass();
$a->test = "one";

$cache->set($a);

$a->test = "two";

$b = $cache->get();

echo $b->test; // I want this to echo one :(