“PHP-like but incompatible” isn’t in itself a useful feature — it is the thing which unlocks a bunch of useful features (a sensible standard library, sensible list/dict datatypes, typed collections, XHP, async functions, generics)

I get that. A superset could be interesting. Downright incompatible seems to tip the balance the wrong way.

PHP is a fractal of bad design[0] and creating a superset will not enable you to create a better language.

[0]: https://eev.ee/blog/2012/04/09/php-a-fractal-of-bad-design/