Does including PHP files that contain functions in it slow the pages with those included even if not being used?

That's basically all my question is, if I have php pages that have 5,000-10,000 lines of code for a certain purpose, in my case image upload management (cropping and such), would it slow down the rest of my documents to include them on each page that doesn't use them? Basic logic tells me it of course would, but at the same time I'm not an expert, so I don't know if php acts differently than I may understand.