phpseclib has 1.5 million monthly downloads on packagist: https://packagist.org/packages/phpseclib/phpseclib/stats So your "no one would ever reimplement it in php and use it in production" comment is misguided.

If you want to do SSH in PHP your options are: phpseclib, SSH via the CLI (which has significant limitations) or libssh2 (which is a PITA to work with and has an API with limited functionality compared to phpseclb).

I'll concede the point that sodium_compat's inability to implement Argon2i isn't of huge concern on PHP 8 or whatever version of PHP might incorporate JIT since that version would also have libsodium but I still contend that it's a perfectly valid example of PHP's fundamental limitations.

I do apologize that I have not done a comprehensive survey of every PHP package ever made so that more examples might be provided.