//When user access token expires user must be logged in and renew the access token him self.it is a Facebook policy
//you can overcome this by sending email to users who have expired access token.
//create a table of successful sending to monitor sending process
//if any failure happened with the user an email is sent to him to ask him to activate there account again.with a link to your subscription page.
//and here is the code should be written on that page.
$app_id = "YOUR_APP_ID";
$app_secret = "YOUR_APP_SECRET";
$my_url = "YOUR_POST_LOGIN_URL";
// known valid access token stored in a database
$access_token = "YOUR_STORED_ACCESS_TOKEN";
$code = $_REQUEST["code"];
// If we get a code, it means that we have re-authed the user
//and can get a valid access_token.
if (isset($code)) {
$token_url="https://graph.facebook.com/oauth/access_token?client_id="
. $app_id . "&redirect_uri=" . urlencode($my_url)
. "&client_secret=" . $app_secret
. "&code=" . $code . "&display=popup";
$response = file_get_contents($token_url);
$params = null;
parse_str($response, $params);
$access_token = $params['access_token'];
}
// Attempt to query the graph:
$graph_url = "https://graph.facebook.com/me?"
. "access_token=" . $access_token;
$response = curl_get_file_contents($graph_url);
$decoded_response = json_decode($response);
//Check for errors
if ($decoded_response->error) {
// check to see if this is an oAuth error:
if ($decoded_response->error->type== "OAuthException") {
// Retrieving a valid access token.
$dialog_url= "https://www.facebook.com/dialog/oauth?"
. "client_id=" . $app_id
. "&redirect_uri=" . urlencode($my_url);
echo("<script> top.location.href='" . $dialog_url
. "'</script>");
}
else {
echo "other error has happened";
}
}
else {
// success
echo("success" . $decoded_response->name);
echo($access_token);
}
// note this wrapper function exists in order to circumvent PHP's
//strict obeying of HTTP error codes. In this case, Facebook
//returns error code 400 which PHP obeys and wipes out
//the response.
function curl_get_file_contents($URL) {
$c = curl_init();
curl_setopt($c, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($c, CURLOPT_URL, $URL);
$contents = curl_exec($c);
$err = curl_getinfo($c,CURLINFO_HTTP_CODE);
curl_close($c);
if ($contents) return $contents;
else return FALSE;
}