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());
