Limit access to FB application by age

I'm looking for a way to limit access to my html FB application to people 开发者_StackOverflow中文版above age limit (let say 16 years). I've found forum topic http://forum.developers.facebook.net/viewtopic.php?pid=123010 but there people have problems to achieve this result.

Any one know working way?

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Here's a method we've used: http://fbdevwiki.com/wiki/Locales#Getting_the_User.27s_Locale

The signed_request has information on country, locale, and age even when the person hasn't logged in. However, I suspect it's limited to only telling you if a person is over 18, 21, or other key ages. It may not give the person's specific age.

edit: The example in the wiki is for the older PHP SDK, I'm not exactly sure how you'd do it in the 3.0 version of the SDK or how it relates to the new OAuth 2.0 change.