Runtime weight of PHP class istantation

I have a question about istantation of classes in PHP.

I have two different situation:

1. I have one file for a class with about 30 method inside like:

class foo
{
function 1 ...
function 2 ...
function 30...
}

2. I have 5 different class with 5 method each like:

class free
{
function 1...
function 5 ...
}

class free_
{
function 1 ...
function 5 ...
}

The question is:
Which is the most weight operation?
Istantatia the first big class and then launch its method or istantiate
the 5 classes and lanuch the specific method?

In this analysys you have to consider that if I instantiate a "small
class", avery method will be launched.
The number of method launched is the same for each situation.

Thanks a lot for any help.