Use static anonymous functions

Will be good to change in all the code and examples.

And explain that's better to use static.

For performance and memory benefit.

> Anonymous functions when declared in the context of a class, the current class is automatically bound to it, making $this available inside of the function's scope. If this automatic binding of the current class is not wanted, then [static anonymous functions](https://www.php.net/manual/en/functions.anonymous.php#functions.anonymous-functions.static) may be used instead.