Facebook user agent

Im trying to put code to recognize facebook user agent, but im dump about php. Could someone help me?
https://developers.facebook.com/docs/opengraph/howtos/maximizing-distribution-media-content/

facebookexternalhit/1.0
facebookexternalhit/1.1

[skoskie]

You could probably go with something like this:

    function filterFacebookBot(array &$userAgent)
    {
        if('facebookexternalhit' === $userAgent['browser_name'])
        {
            $userAgent['browser_name'] = 'facebookbot';
        }
    }

    ///$ua = new ....
    $ua -> addFilter('filterFacebookBot');

It's completely untested, but should be close.