PHP get_headers and curl both give empty result

one text

Solution:

My browser shows warning about that site's HTTPS connection:

The connection to this site uses an obsolete protocol (TLS 1.0), an obsolete key exchange (RSA), and an obsolete cipher (3DES_EDE_CBC with HMAC-SHA1).

So it might simply be that on your system making HTTPS connections with sites that only support outdated security protocols is disabled.

Which Apache config settings regarding SSL are relevant, can be found here: https://superuser.com/a/882651