The effort to move from PHP v4 to v5 is comparable to the Python v2 to v3 move now. A lot of projects did not move to PHP5 for a long time. Lots of libraries ha

The effort to move from PHP v4 to v5 is comparable to the Python v2 to v3 move now. A lot of projects did not move to PHP5 for a long time. Lots of libraries had to be rewritten. The change brought a lot of subtle defects because programmers had unwittingly or knowingly relied on the by-value assignment of objects in PHP4. The PHP Project did manage to allow people to write code that worked on both 4 and 5. At the same time, the project failed to get Unicode in. It's unclear how that will be possible without breaking a lot of programs. If PHP ever switches string handling like Python3 did now, it will be just as painful. Well, that's my prediction anyway, maybe they will figure something out. Just realize that their first try (PHP6) didn't fly at all.