Virtual final classes are helpful in the case someone is wrapping common functions that are static, but the common class itself cannot be instantiated.

There is no need for this function to report errors. Function should have responsibility over a single part of the functionality provided. This change also corrects some error messages.

Let the garbage collector do its job and fix the test.

All methods defined in superclass can be access by $this and $parent construct. There is no need to copy private methods, as they cannot be access in $this context.