Question

This is the code from the canvas tutorial
http://developers.facebook.com/docs/appsonfacebook/tutorial/

This gets the authorization code, redirects the user back to the canvas page and displays the code in the url.

Something like, http://apps.facebook.com/yourapp/?code=1234thecode5678

So, is it possible to do it using ajax and get the code without redirecting? Instead of this method?

Thanks in advance

     $app_id = "YOUR_APP_ID";

     $canvas_page = "YOUR_CANVAS_PAGE_URL";

     $auth_url = "http://www.facebook.com/dialog/oauth?client_id=" 
            . $app_id . "&redirect_uri=" . urlencode($canvas_page);

     $signed_request = $_REQUEST["signed_request"];

     list($encoded_sig, $payload) = explode('.', $signed_request, 2); 

     $data = json_decode(base64_decode(strtr($payload, '-_', '+/')), true);

     if (empty($data["user_id"])) {
            echo("<script> top.location.href='" . $auth_url . "'</script>");
     } else {
            echo ("Welcome User: " . $data["user_id"]);
     } 
 ?>

Answer 1

You can use the Facebook JS SDK to log the user in with out having to refresh or redirect the user.
Taken from the Facebook JS SDK Documentation under the topic FB.login

FB.login(function(response) {
   if (response.authResponse) {
     console.log('Welcome!  Fetching your information.... ');
     FB.api('/me', function(response) {
       console.log('Good to see you, ' + response.name + '.');
       FB.logout(function(response) {
         console.log('Logged out.');
       });
     });
   } else {
     console.log('User cancelled login or did not fully authorize.');
   }
 }, {scope: 'email'});

Note : This is the implementation if you are using oAuth 2.0 (and you really should be). Taken from the same url :

Without OAuth 2.0, scope should instead be replaced with perms, and
response.authResponse replaced with response.session. Remember that
all apps must migrate to OAuth 2.0 by October 1, 2011.