This class no longer exists. The http extension was competely rewritten for version 2.0 and is entirely incompatible with version 1.x. I'm sure it's much improved, but the documentation is useless and offers no help at all upgrading - or more to the point, in rewriting all your code, since almost everything has changed. This is an irresponsible and inadvisable change for whoever allowed this to be released under the same name.