Is there a performance penalty when a class is not found by Composer autoload?

[gskema]

Let's say I have:

<?php

use NotFoundClass;

#[NotFoundClass]
class Acme {
}

Now Acme is within composer class map, but NotFoundClass is not because it's specifically not installed - missing (e.g. using composer replace: *). Will this cause slower performance - e.g. filesystem lookup on each request?

[Seldaek]

By default yes, it will try to look up that class once, but if you use authoritative classmaps then you can skip that.