Object Aggregation

I know this isn't really a PEAR question, but I've tried the general list with little success, and the topic is relevant in that this is pretty much an oop question and this list is more or less the relevant list for that sort of thing. So, here goes... I'm just discovering how I can effectively emulate interfaces using the object aggregation extension. This is a major benefit to me so I'd like to know if others are using this extension. It is marked in the docs as experimental. Does that mean the api might change in PHP4? I'm guessing it won't - I do understand that this extension will be removed in PHP5 but I need this feature now so I'm looking to make use of it. Anyone have an opinion regarding how suitable this extension is in a production environment? I can guarantee that I'll be using at least PHP version 4.4.3 I think if there comes a time I need to port the application to php5, I'll be able to replace the aggregation with actual interfaces. Thoughts? Thanks, Matt.