call one function frome large amount of functions without affect system resource

if I have a lrage amount of functions like 100 function
and I want Organize the code without affect system resource

what the best way like

class {

func1 ()
..
..
func100 ()

}

or

put all functions on one file (functions.php) and when I need one function make include functions.php

if I include class.php or functions.php for execute one function that affect on memory