原文の記事のコメントで、突っ込みの形で結構興味深いコメント付いてるし
結果的にはイイ釣りしたと思う。
Interestingly, the speed of a method call with no parameters was almost exactly the speed of a function call with one parameter.
This is to be expected because the object is a hidden parameter to the method, which becomes the $this variable.