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

How to Determine User Interaction with a Facebook Page via API

You are experiencing difficulties determining whether a user has liked your Facebook page using JavaScript in an iFrame app. While the code you provided seems straightforward, it requires the user to grant extended permission.

An alternative approach is to utilize Facebook's OAuth 2.0 for Canvas advanced option, which allows for the retrieval of a signed_request parameter for each page requested within your tab app. Parsing this parameter provides access to user information, including their liking status.

Here's the revised code:

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;
}

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!";
  }
}

By leveraging the signed_request parameter, you can effectively determine whether a user has interacted with your Facebook page without the need for extended permissions.

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