Criando botão para publicar no twitter, com short url

function bitly()
{
    //login information
    $url = get_permalink();  //generates wordpress' permalink
    $login = 'SEU_BIT_LY_LOGIN';    //your bit.ly login
    $apikey = 'SUA_API_KEY_VAI_AQUI'; //bit.ly apikey
    $format = 'json';   //choose between json or xml
    $version = '2.0.1';

    //create the URL
    $bitly = 'http://api.bit.ly/shorten';
    $param = 'version='.$version.'&longUrl='.urlencode($url).'&login='.$login.'&apiKey='.$apikey.'&format='.$format;

    //get the url
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $bitly . "?" . $param);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    $response = curl_exec($ch);
    curl_close($ch);

    //parse depending on desired format
    if(strtolower($format) == 'json')
    {
        $json = @json_decode($response,true);
        echo $json['results'][$url]['shortUrl'];
    }
    else //xml
    {
        $xml = simplexml_load_string($response);
        echo 'http://bit.ly/'.$xml->results->nodeKeyVal->hash;
    }
}

//Botão do Twitter ficará assim:

<a href="http://twitter.com/home?status=Vale a pena conferir: <?php bitly(); ?> (via @miriamdepaula)" title="Clique aqui para publicar este post no Twitter!" target="_blank" class="twitter-icon">Publicar no Twitter</a>