PHP has been horrible at maintaining the core library. The core library is a guide for developers, as to what their code should look like. (Brian Goetz goes on a long talk about the fact that all of your code is an API, even if you don;t mean it to be)

That's why every time I chastise Scala developers and Martin Odersky for symbolic operator overloading. The guy talks at length about how it's wrong to abuse the symbolic operator overloading in creating unintuitive operators.... and then introduces :$#@%$%$%:;:/ operator to create a list.