function __construct($consumer_key, $consumer_secret, $oauth_token = NULL, $oauth_token_secret = NULL)
{
$this->sha1_method = new OAuthSignatureMethod_HMAC_SHA1();
$this->consumer = new OAuthConsumer($consumer_key, $consumer_secret);
if (!empty($oauth_token) && !empty($oauth_token_secret)) {
$this->token = new OAuthConsumer($oauth_token, $oauth_token_secret);
} else {
$this->token = NULL;
}
}