What is the correct way to set locale on server?

On my development machine (a vagrant box with ubuntu) with a php application runnning I have one language with swedish: sv_SE.utf8

And I'm setting the locale with this function -

setlocale(LC_ALL, 'sv_SE');

And this works, but in production server it didn't. Consider those language settings in production:

sv_SE
sv_SE.iso88591
sv_SE.iso885915
sv_SE.utf8
swedish

When I changed it to

 setlocale(LC_ALL, 'sv_SE.utf8');

..it works. Somehow, the old code retrieves the wrong language, but when I changed it works. But is it correct way to configure the server with all the languages encodings? Wouldn't it be sufficient to just have sv_SE.utf8 - language? Why would you want any else setting? Like sv_SE.iso88591. Seems weird to me.

Know someone who can answer? Share a link to this question via email, Twitter, or Facebook.