For an app I'm developing for Facebook, when the user first logs in, I'd like for my interface to be in the language they have chosen for their Facebook interface.
(More accurately, since Facebook has more language options than I do, I'll see if their language is among my list of languages, and if so use that language. If not, default to English.)
I know I can get the user's locale from the list of columns they keep of user data.
However, I'm unclear if the locale is equal to their language. If an American lives in Beijing, and sets their interface to use English, wouldn't their locale be China? If I go by that, my interface might be in Chinese, which, depending on the American, could be different from their Facebook interface.
I notice on the same list, there is an array of languages that the user can set if they are multilingual, but I'm not sure if that's a really good indicator of anything. People tend to list languages they can only partially speak, so it might not be helpful to try and go through that list.
Bottom line, what exactly should I do to get a Facebook user's interface language from my PHP script in my canvas directory?
The locale setting in this case is the user's currently selected user interface language.
See for yourself in the Graph API Explorer. (Change your own language at the bottom of the page)
Keep in mind that you can access the locale information from the signed request even before the user has authorized your app.
There's no way except locale, also you dont even need an access_token to get locale.