Supporting TLS client certificate in PHP?

[Sean Conner]

It was thus said that the Great Côme Chilliet once stated:
> 
> However, even if I was implementing this in C it is not clear to me how to
> request a client certificate without making it mandatory, is that what
> SSL_VERIFY_CLIENT_ONCE is for? Are there Gemini servers in C with client
> certificate support of which I could read the code out there?

  You might want to check out the source code to LibreSSL (a fork of
OpenSSL).  It comes with a TLS wrapper in the form of libtls (in the tls/
directory), which has the function tlsconf_verify_client_optional().  You
might be able to follow the logic of that function (vs.
tlsconf_verify_client()) to see how it works.

  -spc