integrating with Facebook like

Question

I'd like to integrate the "like" button into my site, but I cannot make sense of the information available on the web. I read this article, which was in another stackoverflow article, but have some questions: http://www.saschakimmel.com/2010/05/how-to-capture-clicks-on-the-facebook-like-button/. I've also posted this question before and the answers I received really had nothing to do with what I was asking. My original question was asked here: Facebook Integration into website.

I've setup a "Page" already in facebook, and from what I understand in the link above, you need to setup an "App" to get an API key. What I don't understand though is that if I use this API Key, it's going to be pointing to my newly created "App", which has no fan base. How do I link this API Key, (or setup another key through the page admin), so I can have users "like" the real facebook page?

I want to run some javascript functions the moment a user likes the page, but I'm also a little confused on what API functions call, and whether these return a true/false value? I only really want to run these js functions if the user has not already liked the page..

Hope this all makes sense, would love any explanations you have to offer to point me in the right direction.

Answer 1

From what I can see, the answers on your other question cover most of what you need to know. The one thing I notice is your comment:

"I am attempting to set a promo code in the background when someone "likes" the page"

There are some tricky terms and conditions surrounding this. Have a look here before continuing: https://developers.facebook.com/docs/guides/policy/examples_and_explanations/Rewarding_Users/

If you start off with adding the like button, then separately you will need to check each logged in facebook user to see if they are connected with your page. You can do this using the api call to get their likes, and checking for your page id in the response:

FB.api('/me/likes', function(response) {
  console.log(response);
});

If you find a match, proceed with your promotion, else show the like button.

Answer 2

What you're trying to do is totally possible, although I usually do that calculation server-side. You may be able to do it via the Javascript SDK, using the basic concept below. Check out this link: http://fbmhell.com/2011/06/facebook-like-gating-in-iframe-tabs/

The basic overview is this:

1. You create a Page
2. You create an app for your promo tab
3. You add the app tab to your page

When the user hits your app tab on your page, Facebook will return a signed request to you.

You can parse out that signed request using a function like this:

function grokSignedRequest() {
    if (isset($_REQUEST['signed_request'])) {
      $encoded_sig = null;
      $payload = null;
      list($encoded_sig, $payload) = explode('.', $_REQUEST['signed_request'], 2);
      $sig = base64_decode(strtr($encoded_sig, '-_', '+/'));
      $data = json_decode(base64_decode(strtr($payload, '-_', '+/'), true));
      return $data;
    }
    return false;
}

As mentioned in that article, if you do a print_r() on that signed request after it's been run through the function provided, you’ll see something like this:

stdClass Object
(
    [algorithm] => HMAC-SHA256
    [issued_at] => 1307627872
    [page] => stdClass Object
        (
            [id] => 116633947708
            [liked] => 1
            [admin] => 1
        )

    [user] => stdClass Object
        (
            [country] => us
            [locale] => en_US
            [age] => stdClass Object
                (
                    [min] => 21
                )
        )
)

From there, you can access the liked parameter, and display content based on whether or not the user has liked the page.

// call the function to parse the signed request
$sr_data = grokSignedRequest();

// check like status
if ($sr_data->page->liked==1) {
    echo 'you are a fan';
} else {
    echo 'you are not a fan.';
}

// check admin status
if ($sr_data->page->admin==1) {
    echo '<li>Dude, you are an ADMIN! BADASS!';
}