Thanks to all for feedback! Let's try to integrate new feature to old class. We have constructor in CURLFile with one required parameter: $filename . To avoid BC break we cannot replace this parameter. So I suggest to do it optional and add setBuffer() method.
So we can create CURLFile with empty parameters in constructor and fill it with setters. Have two more questions: 1) If we not fill all options or fille not compatible options, when we must throw error? ? And what level of this error? (Sorry, I'm just php coder and know about C language and php source so little) For file from disk(or other source) required $filename. For file from buffer required $buffer and $postname. 2) Curently CURLFile cannot be unserialized, because it contains $filename (see source code). How it compatible with our dicussion? Jakub, I think about static factory methods, but not sure if it will be great. I think using empty constructor more clear.
