Replace objects by other objects in-place

Question

Suppose I'd like to build a database abstraction layer, which uses a lazy loading mechanism.

If I ask the layer to load a root object, it loads its external representation and constructs itself.

It then somehow identifies that certain linked objects exist. Since it might be costly to load all up-front, it established proxies for related objects. Such proxies should be able to get passed around.

If a first message is called on such a proxy, it loads its external representation and constructs itself. Since references to the proxy may have been passed around, the created object needs to replace the existing proxy-object in-place.

Can I in-place replace an object with another object in PHP?