Comment by berkes

There should be more interpreters or runtimes. Regardless of the language they are written in. Indeed a rustPHP, maybe a JPHP, cPHP, etc etc. There is zend, but AFAIK that's still using the "official" PHP under the hood. And there is or was hiphop. Not sure how that is going, though.

Because now a vulnerability in PHP affects practically 100% of the users. But with more diversity, it would affect only a part. And if one runtime proves insecure more often than another one, organizations have a choice to move to an interpreter that better fits their security needs.