Hello again, thanks for the explanations I understand enough.

BUT I discovered that it is still possible to serve two different ssl certs for two different domain with only single IP address.

[b]Traditionally[/b] as explained by the previous posts, the [b]setup of vhosts in nginx should be[/b]: (I got lazy to post my nginx server directives so I shortcut it to the following)
domainA + IP-addressA + SSLcertA + port443 and
domainB + IP-addressB + SSLcertB + port443

And the [b]following will be in conflict[/b] as I described in the start topic:
domainA + IP-addressA + SSLcertA + port443 and
domainB + IP-addressA + SSLcertB + port443

[b]But I was able to work on the following configuration as a desperate hack to use two different ssl certs with same IP address by listening to two different ports:[/b]
domainA + IP-addressA + SSLcertA + port443 and
domainB + IP-addressA + SSLcertB + port444

Well, I just need to instruct critical parts of some PHP programs out there to append port 444 on the urls so as not to break urls.

Hehe, I guess its a desperate setup since I'm short of buying either a wildcard ssl OR setup and maintain two cloud server for two domains...