Question

maybe its a tricky question but anyway:

I have a facebook application running on an outside server. Lets say my canvas url is

http://mydomain.com/myapp/

This is integrated into a page, and I can reach the app with an url like

http://facebook.com/mypage/app_123456789

where 123456789 is my Application ID

Users can share certain things on their walls, and that share contains an url back to my app.

So lets say I have a content shared, it has an url like

http://mydomain.com/myapp/content/1

This is where the user goes if he clicks on the wall post.

Now my problem is obviously that I want this url to get redirected back to my facebook PAGE.

It’s easy to redirect everything to

http://facebook.com/mypage/app_123456789

but that takes me to the main page of my application, not to the specific content the user shared.

Is there a way to do this? Like, I can pass a parameter to facebook to tell which page I want to load?

Answer 1

Yes you can! Facebook doesn’t pass any old parameters you give when being redirected to an application’s canvas page, but if you manipulate the parameters in a certain way, you’ll gain access to them.

You’ll have to pass all your parameters in the following format –

https://apps.facebook.com/yourapp?app_data=key1$value1,key2$value2,...

Once you reach your canvas URL, you can retrieve the data in app_data from within the signed_request. Once you have the contents of the parameter, you should have something like this –

key1$value1,key2$value2

Now it is just an issue of parsing that string into an array of keys and values. In this specific example, I’ve chosen a dolar character to separate the keys from the values, but as you can see from the code below, you can use whatever you want to separate the parameters and key/value pairs –

// initialize parameter array
$getParams = array();
$signedRequest = $facebook->getSignedRequest();
// separate each parameter
$app_data = explode(",",$signedRequest['app_data']);
foreach ($app_data as $param_key => $param_value) {
  // separate each key/value pair
  list($key,$value) = explode("$",$param_value);
  $getParams[$key] = $value;
}

At this stage your $getParams array should look something like this

Array(
  'key1'=>'value1',
  'key2'=>'value2'
)

Now that you can pass parameters to your application, you’ll be able to decide what content to show according to the data passed to it from the referring URL.