Example of using PECL's OAuth for PHP

oauth.php

<?php session_start();

define('OAUTH_CONSUMER_KEY', '');
define('OAUTH_CONSUMER_SECRET', '');

define('OAUTH_REQUEST_URL', 'https://api.twitter.com/oauth/request_token');
define('OAUTH_ACCESS_URL', 'https://api.twitter.com/oauth/access_token');
define('OAUTH_AUTHORISE_URL', 'https://api.twitter.com/oauth/authorize');

define('API_URL','http://api.twitter.com/1/');
define('CALLBACK_URL','http://example.com/');

if ( isset($_GET['reset'] ) )
{
unset($_SESSION['token']);
}

try {
	$oauth = new OAuth( OAUTH_CONSUMER_KEY, OAUTH_CONSUMER_SECRET, OAUTH_SIG_METHOD_HMACSHA1, OAUTH_AUTH_TYPE_URI);
	$oauth->enableDebug();
	if (!isset( $_GET['oauth_token'] ) && !isset($_SESSION['token']) )
	{
		$request_token = $oauth->getRequestToken( OAUTH_REQUEST_URL, CALLBACK_URL );
		$_SESSION['secret'] = $request_token['oauth_token_secret'];
		
		header('Location: '. OAUTH_AUTHORISE_URL .'?oauth_token='.$request_token['oauth_token']);
	}
	
	if ( isset($_GET['oauth_token']) && isset($_GET['oauth_verifier']) )
	{
		$oauth->setToken($_GET['oauth_token'], $_SESSION['secret']);
		$access_token = $oauth->getAccessToken( OAUTH_ACCESS_URL );
		
		$_SESSION['token'] = serialize( $access_token );
		
		header('location: /oauth.php');
	}
	
	
	$access_token = unserialize($_SESSION['token']);
	$oauth->setToken( $access_token['oauth_token'], $access_token['oauth_token_secret'] );
	$oauth->fetch( API_URL . 'account/verify_credentials.json' );
	
	echo '<pre>';
	$json = json_decode($oauth->getLastResponse());
	print_r($json);
	

} catch(OAuthException $e) {
	echo '<pre>';
	print_r($e);
}