Problem with complex data structure and sessions

I am new to online PHP communities so if there is a better place to post this please let me know. I may have encountered a bug in PHP 4.0.6, but I don't know where to look to see if it is a known problem, and I have not been able to reproduce the problem in trivial code. I have been programming for a couple decades now, but just started with PHP a few months ago. I've spent a couple months developing a fairly typical catalog / shopping cart / order system for a small web site. My code works flawlessly on 4.0.8 under Windows XP (my development environment), but when I uploaded it to our host (4.0.6 under FreeBSD) it failed in the following way: The Shopping cart (we call it a basket) object includes a two dimensional array of "item" objects indexed by catalog number and package size, and a second array of references to the same item objects. Simplified a little, items are added like this: $this->items[$catalognum][$size] = new BasketItem($catalognum, $size, $quantity); $this->ref[] = &$this->items[$catalognum][$size]; Somewhere in the serialize/store/load/unserialize process handled by the built in session support, $basket->ref[] comes to contain references to arrays rather than references to objects. If I add an "echo $basket->ref[0]" line to a particular page it will print "Object" on the hit that creates the basket, and "Array" when I refresh the page. Under 4.0.8/Windows it will print "Object" each time. This problem causes my code to fail with a "Call to a member function on a non-object" error. Where can I best look to see if this is a known problem? Frank. ----- The very act of seeking sets something in motion to meet us; something in the universe, or in the unconscious responds as if to an invitation. - Jean Shinoda Bolen