/** from codezone4.wordpress.com
url =>https://codezone4.wordpress.com/2013/05/19/codeigniter-facebook-login-tutorial-using-facebook-php-sdk/
**/
function fbtest()
{
$facebook = new Facebook(array('app_id' => '1545133145805354', 'app_secret' => 'e2f35895f03c06a6a757ff30f267dc43', 'default_graph_version' => 'v2.3'));
// Choose your app context helper
$helper = $facebook->getCanvasHelper();
//$helper = $fb->getPageTabHelper();
//$helper = $fb->getJavaScriptHelper();
$signed_in = $helper->getSignedRequest();
// Get the user ID if signed request exists
$user = $signed_in ? $signed_in->getUserId() : null;
print_r($signed_in);
}