Even if autoload is slower, it's such a simple concept that even if you use it early on and need to take it out later, you wouldn't have to restructure anything

Even if autoload is slower, it's such a simple concept that even if you use it early on and need to take it out later, you wouldn't have to restructure anything. If you know performance is that big of a deal upfront, anything bug vanilla PHP might not be the best choice since the interpreter will probably become a bottleneck.