detect whether in facebook environment or not

I am developing a Facebook page and a website which is going to serve its contents to the Facebook page. I am using Zend Framework.

In order to use only one controller both for the website and the Facebook page, I would like to find some way to determine if the c开发者_如何学Pythonurrent user is navigating from Facebook or from the website. Thus, to hide some data if from Facebook and show other if from website.

Which is the best way to do this?

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$_SERVER['HTTP_REFERER'];

If that doesn't answer your question I don't understand what you mean with "navigation from".