The most common defense I hear here is that the inefficiency just never mattered.. and if it did it was because the product was a blockbuster success and you could hire to rewrite the slow parts or adopt hack or whatever.
It does not when your project has not 100s of users hitting at the same time. And honestly, which application survives that at first sight and does not need to solve the problem one level higher (like building for load balancing, writer/read databases, etc ).
I mean, generally what matters is how things scale. This type of slowness is trivially solved with horizontal scaling. Not just that, as a design choice, shared-nothing makes horizontal scaling easier. So this type of slowness isn't really the type that matters, and if anything is actually a net benefit at scale. [Unless you are truly latency-critical, but quite frankly that is pretty rare and php would probably not be the best choice for that at any scale]
