Truncate text to given length with suffixed ellipsis

truncate.php

<?php

/**
 * Truncates text to given length with suffixed ellipsis.
 *
 * @param string $text              Original text string.
 * @param int    $length            Length to truncate to.
 * @param bool   [$wholeWords=true] Whether to truncate back to whole words.
 * @return string Truncated string.
 */
function truncate($text, $length, $wholeWords=true)
{
    if (strlen($text) <= $length) return $text; // no-op

    // if not whole words, simply truncate to length
    if (!$wholeWords) return substr($text, 0, $length).'…';

    // truncate to length+1 (to check if last word is whole)
    $text = substr($text, 0, $length+1);

    // remove trailing truncated word to leave whole words only
    $m = preg_match('/(.+)\b\w+$/', $text, $match);
    $text = $m ? $match[1] : $text;

    // remove any trailing whitespace/punctuation
    // (or trailing extra character if there was only one word)
    $m = preg_match('/(.+)\b\W+$/', $text, $match);
    $text = $m ? $match[1] : substr($text, 0, $length);

    return $text.'…';
}