[development] passing data is free

[Sean Robertson]

> Why not? Passing data around is basically free. You are not copying
> the data, you are creating a reference, deep copy only happens if you
> modify the passed in argument (PHP5 only deep copies an object if you
> instruct it with clone()). So do not hesitate to pass around as many
> data as you want.

How much difference is there in this between PHP4 and PHP5?