Facebook application development Fatal error: Uncaught OAuthException: An active access token must be used

This Topic aplies to SDK 3.x
Subject ( Fatal error: Uncaught OAuthException: An active access token must be used )
The Answer to this problem could be found here : Link
But let's discuss it, shall we!
- There are 4 reasons why Tokens get expire :

1. The token expires after expiration time (2 hours is the default).
2. The user changes his/her password which invalidates the access token.
3. The user DE-authorizes your app.
4. The user logs out of Facebook.

I will not explain the 4 reasons but i will just post the script solution :

	<?php
	$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($c, CURLOPT_SSL_VERIFYPEER, false);
	curl_setopt($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;
	}
	?>

view raw gistfile1.php hosted with ❤ by GitHub

- If there is any question, just post a comment.
- i will get back here to try to explain the codes .

google me (evry1falls)