Twitter API in PHP using codebird - php

Question

I need to incorporate twitter feature in a project of mine. Among all the libraries and wrappers, codebird seemed convenient. I tried to do the basic authentication using codes from their example, but upon uploading the files on the server, i cant get to access them at all. It shows error 500 in server and i cant test them on localhost.
the index.php file
<?php
require_once ('codebird.php');
\Codebird\Codebird::setConsumerKey('123456', '1234567'); // static, see 'Using multiple Codebird instances'
$cb = \Codebird\Codebird::getInstance();
session_start();
if (! isset($_SESSION['oauth_token'])) {
// get the request token
$reply = $cb->oauth_requestToken([
'oauth_callback' => 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']
]);
// store the token
$cb->setToken($reply->oauth_token, $reply->oauth_token_secret);
$_SESSION['oauth_token'] = $reply->oauth_token;
$_SESSION['oauth_token_secret'] = $reply->oauth_token_secret;
$_SESSION['oauth_verify'] = true;
// redirect to auth website
$auth_url = $cb->oauth_authorize();
header('Location: ' . $auth_url);
die();
} elseif (isset($_GET['oauth_verifier']) && isset($_SESSION['oauth_verify'])) {
// verify the token
$cb->setToken($_SESSION['oauth_token'], $_SESSION['oauth_token_secret']);
unset($_SESSION['oauth_verify']);
// get the access token
$reply = $cb->oauth_accessToken([
'oauth_verifier' => $_GET['oauth_verifier']
]);
// store the token (which is different from the request token!)
$_SESSION['oauth_token'] = $reply->oauth_token;
$_SESSION['oauth_token_secret'] = $reply->oauth_token_secret;
// send to same URL, without oauth GET parameters
header('Location: ' . basename(__FILE__));
die();
}
// assign access token on each page load
$cb->setToken($_SESSION['oauth_token'], $_SESSION['oauth_token_secret']);
the callback.php
<?php
require_once ('codebird.php');
\Codebird\Codebird::setConsumerKey('123456', '1234567'); // static, see 'Using multiple Codebird instances'
$cb = \Codebird\Codebird::getInstance();
if(isset($_SESSION['oauth_token'] && isset($_SESSION['oauth_token_secret']))){
$cb->setToken($_SESSION['oauth_token'], $_SESSION['oauth_token_secret']); // see above
$reply = (array) $cb->statuses_homeTimeline();
print_r($reply);
}
else {
echo 'necessary session variables couldnt be found!';
}
?>
This might be a really noob question as i have only basic knowledge in PHP, but any help would be much appriciated, please.