//In Function File

function getTinyUrl($url) {
    $tinyurl = file_get_contents("http://tinyurl.com/api-create.php?url=".$url);
    return $tinyurl;
}

// In Template File

$turl = getTinyUrl(get_permalink($post->ID));
echo 'Tiny Url for this post: <a href="'.$turl.'">'.$turl.'</a>'