Access Token and App Canvas Example

This example covers obtaining an access token and signed request from within the context of an app canvas with the Facebook SDK for PHP.

A signed request will be sent to your app via the HTTP POST method within the context of app canvas. The PHP SDK provides a helper to easily obtain, validate & decode the signed request. If the proper OAuth data exists in the signed request payload data, an attempt can be made to obtain an access token from the Graph API.

$fb = new Facebook\Facebook([

‘app_id’ => ‘{app-id}’,

‘app_secret’ => ‘{app-secret}’,

‘default_graph_version’ => ‘v2.10’,

]);

$helper = $fb->getCanvasHelper();

try {

$accessToken = $helper->getAccessToken();

} catch(Facebook\Exceptions\FacebookResponseException $e) {

// When Graph returns an error

echo ‘Graph returned an error: ‘ . $e->getMessage();

exit;

} catch(Facebook\Exceptions\FacebookSDKException $e) {

// When validation fails or other local issues

echo ‘Facebook SDK returned an error: ‘ . $e->getMessage();

exit;

}

if (! isset($accessToken)) {

echo ‘No OAuth data could be obtained from the signed request. User has not authorized your app yet.’;

exit;

}

// Logged in

echo ‘<h3>Signed Request</h3>’;

var_dump($helper->getSignedRequest());

echo ‘<h3>Access Token</h3>’;

var_dump($accessToken->getValue());