Fix $_SERVER['SERVER_PORT'] handling
While installing Framadate on Apache, but proxyfied by an Nginx, $_SERVER['SERVER_PORT'] failed to be correctly handled.
$_SERVER['SERVER_PORT'] is then a string and not an integer, so it was added in the response of get_server_name() function, breaking all the css/js links.
I don't know if there is other situations where the bug appears.
Schema of the installation:
Nginx (443) -> Apache2 (80) + Framadate
Please note that using port 80 on Nginx worked.