Question

I am using Twitter to log users into to a website, which seems to be working up until I attempt to obtain a valid Access Token.

require("twitteroauth.php");
require 'twconfig.php';
session_start();

$twitteroauth = new TwitterOAuth(YOUR_CONSUMER_KEY, YOUR_CONSUMER_SECRET);
$request_token = $twitteroauth->getRequestToken('http://****/tw_response.php');

$oauth_token = $request_token['oauth_token'];
$_SESSION['oauth_token'] = $oauth_token;

$oauth_token_secret = $request_token['oauth_token_secret'];
$_SESSION['oauth_token_secret'] = $oauth_token_secret;

if ($twitteroauth->http_code == 200) {
    url = $twitteroauth->getAuthorizeURL($request_token['oauth_token']);
    header('Location: '.$url);
} else {
    die('Something wrong happened.');
}

This seems to be working correctly, redirecting me to twitter to sign in and confirm access, after which it returns me to tw_response.php (my Callback url), with the following variables in the url:

http://example.com/login.php?oauth_token=sO3X...yj0k&oauth_verifier=Ip6T...gALQ 

In tw_response.php I then try to get the Access Token, but it reports as invalid. I tried using var_dump to view the content of the access token as follows:

require("twitteroauth.php");
require 'twconfig.php';
session_start();

$oauth_verifier = $_REQUEST['oauth_verifier'];
$oauth_token = $_SESSION['oauth_token'];
$oauth_token_secret = $_SESSION['oauth_token_secret'];

$twitteroauth = new TwitterOAuth(YOUR_CONSUMER_KEY, YOUR_CONSUMER_SECRET, $oauth_token, $oauth_token_secret);

$access_token = $twitteroauth->getAccessToken($data['oauth_verifier']);
var_dump($access_token);

The result of the var_dump ends in “invalid / expired Token”:

array(8) {
    ["oauth_url"] => string(104) ""1.0" encoding="UTF-8"?>/oauth/access_token?oauth_consumer_key=ceE...9Dg"
    ["oauth_nonce"]=> string(32) "c52...d07"
    ["oauth_signature"]=> string(28) "ry7...Fcc="
    ["oauth_signature_method"]=> string(9) "HMAC-SHA1"
    ["oauth_timestamp"]=> string(10) "1359031586"
    ["oauth_token"]=> string(40) "sO3...j0k"
    ["oauth_verifier"]=> string(43) "Ip6...ALQ"
    ["oauth_version"]=> string(63) "1.0 Invalid / expired Token "
}

Answer 1

$access_token = $twitteroauth->getAccessToken($data['oauth_verifier']);
var_dump($access_token);

Where did $data magically come from? You have the variable $oauth_verifier, but keep in mind you don’t need this if this is your registered callback URL.

Since you used an invalid variable inside getAccessToken, it will return an invalid value back.

The correct way to use TwitterOAuth:

if (!isset($_GET["oauth_token"])) {
    // set these values in a config file somewhere.
    $twitter = new TwitterOAuth(CONSUMER_KEY, CONSUMER_SECRET);

    // append a ?. This is your callback URL if you specify something.
    $credentials = $twitter->getRequestToken("http://example.com/test.php?");

    // try and be a bit more elegant with the URL... This is a minimal example
    $url = $twitter->getAuthorizeUrl($credentials);
    echo $url;

    // these are temporary tokens that must be used to fetch the new,
    // permanent access tokens. store these in some way,
    // session is a decent choice.
    $_SESSION["token"] = $credentials["oauth_token"];
    $_SESSION["secret"] = $credentials["oauth_token_secret"];
} else {

    // use the user's previously stored temporary credentials here
    $twitter = new TwitterOAuth(CONSUMER_KEY, CONSUMER_SECRET,
                    $_SESSION["token"], $_SESSION["secret"]);

    // uses the oauth_token (from the request) already.
    // you store these credentials in your database (see below).
    $credentials = $twitter->getAccessToken($_GET["oauth_verifier"]);

    // just a printout of credentials. store these, don't display them.
    echo "<pre>";
    var_dump($credentials);
    // valid credentials, provided you give the app access to them.
    echo "</pre>";
}

I just use a single script for callbacks for ease of use; you can split the relevant sections into multiple scripts if you like (and you probably should).

Handily for your database, the credentials include the twitter user’s username, too.
Edit: Twitter is now allocating 64bit integers for user IDs. You should store this as a string to ensure that you don’t end up with mangled user IDs and collisions if you can’t handle 64bit integers in every part of your application.

array(4) {
  ["oauth_token"]=>
  string(50) "7041...wYupkS"
  ["oauth_token_secret"]=>
  string(42) "O9ENq...21B2fk"
  ["user_id"]=> // user ID. always the same, never changes (store this as ID)
  string(9) "..."
  ["screen_name"]=> // username. can change.
  string(11) "..."
}

So, if you want to log users in through twitter, without explicitly giving them a login to your site, you could use $_SESSION (I use databases for my logins, which is recommended if you want to save that state)
In the above script you would add this to the end of the else block:

$_SESSION["token"] = $credentials["oauth_token"];
$_SESSION["secret"] = $credentials["oauth_secret"];
$_SESSION["username"] = $credentials["screen_name"];

You can also get the user’s screen name and more from GET account/verify_credentials, if you want to give them a user page (if you use javascript, grab their userid through id_str here):

$user_array = $twitter->get("account/verify_credentials");