Look at Py3 vs Py2.
At the end of the day, the way I see it, the true advantage of PHP was its lower barrier to entry. Now that this has mostly been resolved via PaaS hosting, it seems to me we're moving to a word where Node is the new default, because Javascript.
But it was cleaned up, and mostly incompatible - after all all the commands had changed from cvs to svn :)
A cleaned up PHP would be interesting but it would need a truly killer app. Basically make a PHP clone except for the bad parts. I'd say that the killer app would be a very to use framework that provided various security best practices already built in.
And a PHP clone would need a 0 installation process - no messing around with shell commands or root access. Just copy your .phpclone files and you're set to go.
The big thing PHP has going for it is the huge amount of open source software, and the number of webhosts which support PHP by default. Most of the webhosts can barely keep PHP updated, and the ones who don't, justify it by wanting to avoid breaking backward compatibility with open source software.
Getting widespread adoption for a PHP alternative would be a serious feat.
> I'm proud to release the result of a Facebook-sponsored study on the feasibility of using the RPython toolchain to produce a PHP interpreter. The rules were simple: two months; one person; get as close to PHP as possible, implementing enough warts and corner cases to be reasonably sure that it answers hard problems in the PHP language. The outcome is called Hippy VM and implements most of the PHP 1.0 language (functions, arrays, ints, floats and strings).
I don't mean a Ruby or another vastly different language.
I mean a language similar in approach to PHP, but with the gotcha's removed, some order and consistency introduced into the API, and a few changes to the defaults. Open source, free, and on all major OS's.