I am creating a PHP website and it contains several sections, I was wondering is it safe to keep all of my functions in 1 file and then **include it in every other file**? 

It would certainly make things easier for me but do you think it's a good idea? In both **security** aspects and **speed**. Because if I keep all my functions in a single page it would definitely become quite big, and I wouldn't be needing a lot of them in a lot of pages, so, wouldn't it affect my script's speed? 

And do you think it's wise to keep all of them together? Aren't I just making it easier for hackers to find the core of my script? What do you suggest I should do?