get_current_site() showing "main" site information only

[kegster]

I have a custom theme that i placed var_dump(get_current_site()); in the header.php of the twenty eleven theme and installed it on 3 sites on my multisite. On each site, regardless which one or logged in or not, the var_dump displayed the $current_site of the "main" site. (domain.com). test1.domain.com, test2.domain.com, etc all showed the information for domain.com. I cannot grab the correct site ID. I even did a fresh multisite install with just twentyeleven and had these problems.

Sounds like you need get_current_blog_id(), get_blog_details(), or $current_blog global instead.

that works actually, but why does get_current_site not work?

get_current_site() was inherited from MU, and the terminology was different then:
​http://nacin.com/2010/03/25/terminology-nightmare-blogs-sites-networks/

$current_blog refers to the current site (in 3.0+ terms), and $current_site refers to the whole network.