Facebook how to check if user has liked page and show content?

I am trying to create a Facebook iFrame app. The app should first show an image and if the user likes the page, he will get access to some content.

I use RoR, therefore I can't use the Facebook PhP SDK.

Here is my iFrame HTML when the user has not liked the page:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<link rel="stylesheet" type="text/css" href="style.css" />
<style type="text/css">
body {
width:520px;
margin:0; padding:0; border:0;
font-family: verdana;
background:url(repeat.png) repeat;
margin-bottom:10px;
}
p, h1 {width:450px; margin-left:50px; color:#FFF;}
p {font-size:11px;}
</style>
<meta http-equiv="Content-Type" content="text/html;
charset=iso-8859-1" />
</head>
<body>
<div id="container">
<img src="welcome.png" alt="Frontimg">
</div>

And, if the user has liked the page:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<link rel="stylesheet" type="text/css" href="style.css" />
<style type="text/css">
body {
width:520px;
margin:0; padding:0; border:0;
font-family: verdana;
background:url(repeat.png) repeat;
margin-bottom:10px;
}
p, h1 {width:450px; margin-left:50px; color:#FFF;}
p {font-size:11px;}
</style>
<meta http-equiv="Content-Type" content="text/html;
charset=iso-8859-1" />
</head>
<body>
<div id="container">
<img src="member.png" alt="Frontimg">
<p>You liked this page</p>

Answers:

Answer

UPDATE 21/11/2012 @ALL : I have updated the example so that it works better and takes into accounts remarks from Chris Jacob and FB Best practices, have a look of working example here


Hi So as promised here is my answer using only javascript :

The content of the BODY of the page :

<div id="fb-root"></div>
<script src="http://connect.facebook.net/en_US/all.js"></script>
<script>
  FB.init({
    appId  : 'YOUR APP ID',
    status : true, 
    cookie : true, 
    xfbml  : true  
  });
</script>

<div id="container_notlike">
YOU DONT LIKE
</div>

<div id="container_like">
YOU LIKE
</div>

The CSS :

body {
width:520px;
margin:0; padding:0; border:0;
font-family: verdana;
background:url(repeat.png) repeat;
margin-bottom:10px;
}
p, h1 {width:450px; margin-left:50px; color:#FFF;}
p {font-size:11px;}

#container_notlike, #container_like {
    display:none
}

And finally the javascript :

$(document).ready(function(){

    FB.login(function(response) {
      if (response.session) {

          var user_id = response.session.uid;
          var page_id = "40796308305"; //coca cola
          var fql_query = "SELECT uid FROM page_fan WHERE page_id = "+page_id+"and uid="+user_id;
          var the_query = FB.Data.query(fql_query);

          the_query.wait(function(rows) {

              if (rows.length == 1 && rows[0].uid == user_id) {
                  $("#container_like").show();

                  //here you could also do some ajax and get the content for a "liker" instead of simply showing a hidden div in the page.

              } else {
                  $("#container_notlike").show();
                  //and here you could get the content for a non liker in ajax...
              }
          });


      } else {
        // user is not logged in
      }
    });

});

So what what does it do ?

First it logins to FB (if you already have the USER ID, and you are sure your user is already logged in facebook, you can bypass the login stuff and replace response.session.uid with YOUR_USER_ID (from your rails app for example)

After that it makes a FQL query on the page_fan table, and the meaning is that if the user is a fan of the page, it returns the user id and otherwise it returns an empty array, after that and depending on the results its show a div or the other.

Also there is a working demo here : http://jsfiddle.net/dwarfy/X4bn6/

It's using the coca-cola page as an example, try it go and like/unlike the coca cola page and run it again ...

Finally some related docs :

FQL page_fan table

FBJS FB.Data.query

Don't hesitate if you have any question ..

Cheers

UPDATE 2

As stated by somebody, jQuery is required for the javascript version to work BUT you could easily remove it (it's only used for the document.ready and show/hide).

For the document.ready, you could wrap your code in a function and use body onload="your_function" or something more complicated like here : Javascript - How to detect if document has loaded (IE 7/Firefox 3) so that we replace document ready.

And for the show and hide stuff you could use something like : document.getElementById("container_like").style.display = "none" or "block" and for more reliable cross browser techniques see here : http://www.webmasterworld.com/forum91/441.htm

But jQuery is so easy :)

UPDATE

Relatively to the comment I posted here below here is some ruby code to decode the "signed_request" that facebook POST to your CANVAS URL when it fetches it for display inside facebook.

In your action controller :

decoded_request = Canvas.parse_signed_request(params[:signed_request])

And then its a matter of checking the decoded request and display one page or another .. (Not sure about this one, I'm not comfortable with ruby)

decoded_request['page']['liked']

And here is the related Canvas Class (from fbgraph ruby library) :

 class Canvas

    class << self
      def parse_signed_request(secret_id,request)
        encoded_sig, payload = request.split('.', 2)
        sig = ""
        urldecode64(encoded_sig).each_byte { |b|
          sig << "%02x" % b
        }
        data = JSON.parse(urldecode64(payload))
          if data['algorithm'].to_s.upcase != 'HMAC-SHA256'
          raise "Bad signature algorithm: %s" % data['algorithm']
        end
        expected_sig = OpenSSL::HMAC.hexdigest('sha256', secret_id, payload)
        if expected_sig != sig
          raise "Bad signature"
        end
        data
      end

      private

      def urldecode64(str)
        encoded_str = str.gsub('-','+').gsub('_','/')
        encoded_str += '=' while !(encoded_str.size % 4).zero?
        Base64.decode64(encoded_str)
      end
    end  

 end
Answer

You need to write a little PHP code. When user first click tab you can check is he like the page or not. Below is the sample code

include_once("facebook.php");

    // Create our Application instance.
    $facebook = new Facebook(array(
      'appId'  => FACEBOOK_APP_ID,
      'secret' => FACEBOOK_SECRET,
      'cookie' => true,
    ));

$signed_request = $facebook->getSignedRequest();

// Return you the Page like status
$like_status = $signed_request["page"]["liked"];

if($like_status)
{
    echo 'User Liked the page';
    // Place some content you wanna show to user

}else{
    echo 'User do not liked the page';
    // Place some content that encourage user to like the page
}
Answer

With Javascript SDK, you can change the code as below, this should be added after FB.init call.

     // Additional initialization code such as adding Event Listeners goes here
FB.getLoginStatus(function(response) {
      if (response.status === 'connected') {
        // the user is logged in and has authenticated your
        // app, and response.authResponse supplies
        // the user's ID, a valid access token, a signed
        // request, and the time the access token 
        // and signed request each expire
        var uid = response.authResponse.userID;
        var accessToken = response.authResponse.accessToken;
        alert('we are fine');
      } else if (response.status === 'not_authorized') {
        // the user is logged in to Facebook, 
        // but has not authenticated your app
        alert('please like us');
         $("#container_notlike").show();
      } else {
        // the user isn't logged in to Facebook.
        alert('please login');
      }
     });

FB.Event.subscribe('edge.create',
function(response) {
    alert('You liked the URL: ' + response);
      $("#container_like").show();
}
Answer

There is an article here that describes your problem

http://www.hyperarts.com/blog/facebook-fan-pages-content-for-fans-only-static-fbml/

    <fb:visible-to-connection>
       Fans will see this content.
       <fb:else>
           Non-fans will see this content.
       </fb:else>
    </fb:visible-to-connection>
Answer

Here's a working example, which is a fork of this answer:

$(document).ready(function(){
    FB.login(function(response) {
        if (response.status == 'connected') {
            var user_id = response.authResponse.userID;
            var page_id = "40796308305"; // coca cola page https://www.facebook.com/cocacola
            var fql_query = "SELECT uid FROM page_fan WHERE page_id="+page_id+" and uid="+user_id;

            FB.api({
                method: 'fql.query',
                query: fql_query
            },
            function(response){
                if (response[0]) {
                    $("#container_like").show();
                } else {
                    $("#container_notlike").show();
                }
            }
            );    
        } else {
        // user is not logged in
        }
    });
});

I used the FB.api method (JavaScript SDK), instead of FB.Data.query, which is deprecated. Or you can use the Graph API like with this example:

$(document).ready(function() {
    FB.login(function(response) {
        if (response.status == 'connected') {
            var user_id = response.authResponse.userID;
            var page_id = "40796308305"; // coca cola page https://www.facebook.com/cocacola
            var fql_query = "SELECT uid FROM page_fan WHERE page_id=" + page_id + " and uid=" + user_id;

            FB.api('/me/likes/'+page_id, function(response) {
                if (response.data[0]) {
                    $("#container_like").show();
                } else {
                    $("#container_notlike").show();
                }
            });
        } else {
            // user is not logged in
        }
    });
});?
Answer

There are some changes required to JavaScript code to handle rendering based on user liking or not liking the page mandated by Facebook moving to Auth2.0 authorization.

Change is fairly simple:-

sessions has to be replaced by authResponse and uid by userID

Moreover given the requirement of the code and some issues faced by people(including me) in general with FB.login, use of FB.getLoginStatus is a better alternative. It saves query to FB in case user is logged in and has authenticated your app.

Refer to Response and Sessions Object section for info on how this might save query to FB server. http://developers.facebook.com/docs/reference/javascript/FB.getLoginStatus/

Issues with FB.login and its fixes using FB.getLoginStatus. http://forum.developers.facebook.net/viewtopic.php?id=70634

Here is the code posted above with changes which worked for me.

$(document).ready(function(){
    FB.getLoginStatus(function(response) {
        if (response.status == 'connected') {
            var user_id = response.authResponse.userID;
            var page_id = "40796308305"; //coca cola
            var fql_query = "SELECT uid FROM page_fan WHERE page_id =" + page_id + " and uid=" + user_id;
            var the_query = FB.Data.query(fql_query);

            the_query.wait(function(rows) {

                if (rows.length == 1 && rows[0].uid == user_id) {
                    $("#container_like").show();

                    //here you could also do some ajax and get the content for a "liker" instead of simply showing a hidden div in the page.

                } else {
                    $("#container_notlike").show();
                    //and here you could get the content for a non liker in ajax...
                }
            });
        } else {
            // user is not logged in
        }
    });

});

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