facebook app authorizing: An error occurred. Please try again later - php

Question

I’ve just created a Facebook app, this is my first attempt and I followed Facebook developer’s documentation totally, while completing everything as stated I am stucked at this error while authorizing app:
An error occurred. Please try again later.
<?php
$app_id = '1603369454518730';
$app_secret = '511b194f6sdgg6eca7cc748d7be6d82d';
//$canvas_page = "http://apps.facebook.com/myapp";
$canvas_page = "http://myappweb.com/app/landhere.php";
$auth_url = "https://www.facebook.com/dialog/oauth?client_id=" . $app_id . "&redirect_uri= " . urlencode($canvas_page);
//Requesting Signed Parameter:
$signed_request = $_REQUEST["signed_request"];
list($encoded_sig, $payload) = explode('.', $signed_request, 2);
$data = json_decode(base64_decode(strtr($payload, '-_', '+/')), true);
//User Info. Variables:
try {
$userId = $data["user_id"];
} catch(Exception $e) {
echo $e -> getMessage();
echo "<br>";
}
if (!empty($data["user_id"])) {
if ($data['page']['liked']) {
echo "hello";
} else {
echo "like page";
}
} else {
echo("<script> top.location.href='" . $auth_url . "'</script>");
}
?>
Ive tried suggestion that I found in other threads such as checking app id and app secret, disabling sandbox. But none of this has worked yet for me. Kindly help me with this.
Thank you.

Answer 1

I'm not into coding too much, but kinda sorted it out.
Your canvas page should be the url of the page not your app url.
Also I tried using the following code and it works.
<?php
$app_id = "APP_ID";
$canvas_page = "CANVAS_PAGE";
$auth_url = "http://www.facebook.com/dialog/oauth?client_id="
. $app_id . "&redirect_uri=" . urlencode($canvas_page);
$signed_request = $_REQUEST["signed_request"];
list($encoded_sig, $payload) = explode('.', $signed_request, 2);
$data = json_decode(base64_decode(strtr($payload, '-_', '+/')), true);
if (empty($data["user_id"])) {
echo("<script> top.location.href='" . $auth_url . "'</script>");
} else {
echo ("Welcome User: " . $data["user_id"]);
}
?>

Answer 2

If I'm not mistaken, (My interaction with the PHP SDK is minimal), you need to add a redirection url to which FB will return when authentication is complete, to acomplish that you will have to do two steps:
1) $auth_url = "http://www.facebook.com/dialog/oauth?client_id="
. $app_id . "&redirect_uri=" . urlencode($canvas_page);
2) In you'r applications' page: https://developers.facebook.com/apps/app_id
press Edit and in "Select how your app integrates with Facebook"
select Website.
put in the URL the you'r http://apps.facebook.com/myapp.
good luck