Facebook app special gifts implementation? - facebook

Question

Example: Bejeweled Blitz frequently runs events and promotions that, when clicked, take you to their app page. Once there, the app can see that the page was reached by following the promotional link and forks over the reward.
How is this done? What do I need to do to implement a similar feature? To my knowledge the parent URL is out of bounds due to the domains being different (Facebook vs. my app), so how is the message passed to the app?

Answer 1

Every app (Canvas, Page tab)
You can get data by passing an app_data parameter to any URL linking to a Facebook app. This parameter value will then be added to the signed_request.
As so, this url http://facebook.com/mypage/app_123?app_data=promotion12 will allow you to get promotion12 via the signed_request.
In PHP, this would give you something like this:
$signed_request = $facebook->getSignedRequest();
$app_data = $signed_request['app_data'];
Of course, you could pass any string by there; for example it could be a JSON string.
That's really the heart of getting data from outside to inside an app.
Hope this help you out!
Canvas app
In Canvas app however, it's much simpler, every query parameter will be passed to the app.
So, http://apps.facebook.com/myapp?somedata=hey can be get via:
$data = $_GET['somedata'];
Facebook will just append those parameter to the iframe URL.
Docs
https://developers.facebook.com/docs/reference/login/signed-request/ (was pretty hard to find, damn FB documentation)

Answer 2

This is done with the query parameters passed in the URL that users click on. A clear example is DoubleDownCasino sharing an URL for their users to click on. The link is:
http://apps.facebook.com/doubledowncasino/?pid=PNNTDP&target_url=pid%3APNNTDP
What DoubleDownCasino probably does is once their canvas app loads, they parse the URL for the query params and the pid and target_url parameters help determine what type of "reward" the user gets. Once they redeem it, clicking the same URL won't get the reward again because it can check if the user has already redeemed the offer with the given pid and target_url.
Your question:
Example: Bejeweled Blitz frequently runs events and promotions that, when clicked, take you to their app page. Once there, the app can see that the page was reached by following the promotional link and forks over the reward.
What I explained above is exactly how Bejweled Blitz does it in this post. If you follow through the bit.ly short URL, the URL is:
http://apps.facebook.com/bejeweledblitz/?zgift=0/eTtVUuhF5ipdJmO1jlDhr96MtKjp1NYflJrcOddB6iZDH1y96K%2Bml6gC0%2B5yVN
So answering your question, Bejeweled Blitz run promotions and rewards by appending query parameters, which in this case is zgift, which they can then parse in their app by getting the current URL the user is hitting.