Cannot getUser() in the canvas page using PHP SDK - facebook-graph-api

Question

I am quite confused using the Facebook application in the iframe. I granted permissions to the app and accessed to it, but the application acts very strange. If I try to test myself withe the code:
$app = array(
'appId' => 'yyy',
'secret' => 'xxx',
'cookie' => true
);
$facebook = new Facebook($app);
$user_id = $facebook->getUser();
I get 0. On the other hand, if I use this kind of code:
$canvas_page = 'http://www.bandito.sk/facebook/canvas.php';
$auth_url = "https://www.facebook.com/dialog/oauth?client_id="
. $app_id . "&redirect_uri=" . urlencode($canvas_page)."&scope=user_about_me,user_birthday,email,user_status";
$signed_request = $_REQUEST["signed_request"];
list($encoded_sig, $payload) = explode('.', $signed_request, 2);
$data = json_decode(base64_decode(strtr($payload, '-_', '+/')), true);
I get all what I need. But I just don't understand, the Facebook doesn't even send a signedRequest() in the first example. Do I have to login even tough I use the application inside Facebook as a canvas page?

Answer 1

OK found it on my own
$request_ids = explode(',', $_REQUEST['request_ids']);
print_r($request_ids);
foreach($request_ids AS $request_id){
$request_uri=$request_id."_".$data[user_id];
$ch = curl_init('https://graph.facebook.com/'.$request_uri.'&access_token='.$data[oauth_token]);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "DELETE");
$response = curl_exec($ch);
var_dump($response)."<br>";
}