How Can I Check if a Facebook User Liked My Page Using the API?

Identifying Facebook Page Likes Using API

Facebook's API provides a method to determine if a user has liked a specific page or URL. Here's a JavaScript code snippet that demonstrates how to use this functionality:

FB.api({
    method:     "pages.isFan",
    page_id:        my_page_id,
},  function(response) {
        console.log(response);
        if(response){
            alert('You Likey');
        } else {
            alert('You not Likey :(');
        }
    }
);

While this code seems straightforward, it may not always return the expected result. This is because the 'pages.isFan' method requires the user to have granted an extended permission for the app, which may not be acceptable in all cases.

Alternative Approach Using Signed Request

An alternative approach to checking page likes is to use the OAuth 2.0 for Canvas advanced option. When enabled, Facebook includes a 'signed_request' parameter in the page request. This parameter can be parsed to obtain information about the user, including whether they have liked the page.

Here's an example of a PHP function that parses the signed request:

function parsePageSignedRequest() {
    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;
  }

Using this function, you can then check the 'page.liked' property in the returned data:

if($signed_request = parsePageSignedRequest()) {
    if($signed_request->page->liked) {
      echo "This content is for Fans only!";
    } else {
      echo "Please click on the Like button to view this tab!";
    }
  }

This approach provides a more reliable way to determine page likes without requiring additional permissions.

The above is the detailed content of How Can I Check if a Facebook User Liked My Page Using the API?. For more information, please follow other related articles on the PHP Chinese website!