add ... if longer than what is shown

<?php echo substr($category_topic_list[$i]["title"],0,20); ?>

If the title is longer than 20 characters, I'd like it to add "..." to the end to show that the title is longer than what is shown. Can this be done?

<?php
if (strlen($category_topic_list[$i]["title"]) > 20) {
echo substr($category_topic_list[$i]["title"],0,20) . "...";
} else {
echo $category_topic_list[$i]["title"];
}
?>

Makes perfect sense, don't know why I didn't think of that. Thank you so much!