Facebook App for adding tab to page OAuth in Codeigniter - php

Question

I am creating a facebook app for adding a tab on my facebook page. I am using Codeigniter Framework for that. I need access to some user info - email, education, etc in a particular page of my app. So, I need to authenticate only in that page and get the access token. In my attempt of doing that I am able to authenticate the user but unable to get the code sent by facebook oauth, which I need to get the access token. I think this is due to the fact that Codeigniter modifies the get array. I tried some ways to get the get array working but I was still unable to get the code contents.
Can you please give me a straight forward way to get an oauth token for the user in my app. I have tried to search a lot, but nothing worked.
So far this is the code I wrote:
$canvas_page = $page_url;
$signed_request = $_REQUEST["signed_request"];
$code = $this->input->get('code');
list($encoded_sig, $payload) = explode('.', $signed_request, 2);
$data = json_decode(base64_decode(strtr($payload, '-_', '+/')), true);
$auth_url = "https://www.facebook.com/dialog/oauth?client_id=" . $app_id . "&redirect_uri=" . urlencode($canvas_page)."&scope=email,user_work_history,user_education_history";
if (empty($data["user_id"])) {
echo("<script> top.location.href='" . $auth_url . "'</script>");
} else {
echo ("Welcome User: " . $data["user_id"])."<br/>";
$token_url = "https://graph.facebook.com/oauth/access_token?". "client_id=" . $app_id . "&redirect_uri=" . urlencode($canvas_page). "&client_secret=" . $app_secret . "&code=" . $code;
$a = file_get_contents($graph_url);
var_dump($a);
}
Please give me a simple way to get the OAuth done. I want to spend more time developing that app than trying to figure out OAuth.

Answer 1

You may disable sanitization of GET but you probably doesn't want this.
As a quick and dirty solution you can do something like this:
parse_str($_SERVER['QUERY_STRING'], $args); // $args now contain GET parameters