Services_Twitter Pear PHP code - OAuth direct messages suddenly stopped working - php

Question

I have the following PHP code, which up to a week or so ago was working to send Twitter direct messages to a particular user. I now get "HTTP_OAuth_Exception: Unable to connect to tcp://api.twitter.com:80. Error #0: php_network_getaddresses: getaddrinfo failed: Name of service not known in /usr/share/pear/HTTP/OAuth/Consumer.php on line 257"
I've searched around and can't find that anything has changed with Twitter since it was working and the server configuration also hasn't changed. I tried using SSL in case Twitter suddenly required connection via SSL, but that gave basically the same error (except it said ssl and port 443).
I'm at a loss to see what's wrong and don't believe anything changed on my side. My code is based on the example in the Services_Twitter documentation (http://pear.php.net/package/Services_Twitter/docs/latest/Services_Twitter/Services_Twitter.html#var$oauth)
Any help would be greatly appreciated.
require_once 'Services/Twitter.php';
require_once 'HTTP/OAuth/Consumer.php';
$twitterto = 'xxxxxxxxxxxx';
$message='This is a test message';
$cons_key='xxxxxxxxxxxx';
$cons_sec='xxxxxxxxxxxx';
$auth_tok='xxxxxxxxxxxx';
$tok_sec='xxxxxxxxxxxx';
try {
$twitter = new Services_Twitter();
$oauth = new HTTP_OAuth_Consumer($cons_key,
$cons_sec,
$auth_tok,
$tok_sec);
$twitter->setOAuth($oauth);
// The error is raised on the following line.
$twitter->direct_messages->new($twitterto, $message);
$twitter->account->end_session();
} catch (Services_Twitter_Exception $e) {
echo $e->getMessage();
}