Sign in with Twitter

<?php

define('TWITTER_OAUTH_CONSUMER_KEY','your consumer key');
define('TWITTER_OAUTH_CONSUMER_SECRET','your consumer secret');

require('twitteroauth/twitteroauth.php');//search for "twitter api 1.1" and dowload

session_start();

if(!empty($_GET['oauth_verifier']) && !empty($_SESSION['oauth_token']) && !empty($_SESSION['oauth_token_secret'])) {
    $twoauth = new TwitterOAuth(TWITTER_OAUTH_CONSUMER_KEY, TWITTER_OAUTH_CONSUMER_SECRET, $_SESSION['oauth_token'], $_SESSION['oauth_token_secret']);
    $access_token = $twoauth->getAccessToken($_GET['oauth_verifier']);
    $_SESSION['access_token'] = $access_token;
    $user_info = $twoauth->get('account/verify_credentials');

    echo("<pre>");
    print_r($user_info);
    echo("</pre>");

} else {

    $twoauth = new TwitterOAuth(TWITTER_OAUTH_CONSUMER_KEY,TWITTER_OAUTH_CONSUMER_SECRET);

    $request_token = $twoauth->getRequestToken('http://yourpage.com/name_of_this_page.php');

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

    if ($twoauth->http_code == 200) {
        $url = $twoauth->getAuthorizeURL($request_token['oauth_token']);
        header("Location: " . $url);
    } else {
        die("oops... something's wrong!");
    }
}