truncate.php

<?php
    /**
     * @param string $message
     * @param int $length
     * @param string $cap What to place at the end of the truncated message to indicate truncation.
     * @param string $delimiter
     * @param bool $removeLastDelimiter
     * @param bool $lengthInBytes
     * @param string|null $encoding
     * @return string
     */
    function truncate(string $message, int $length, string $cap, string $delimiter = ' ', bool $removeLastDelimiter = true, bool $lengthInBytes = false, string $encoding = null): string
    {
        if ($encoding === null) {
            $encoding = mb_internal_encoding();
        }

        if (($lengthInBytes ? strlen($message) : mb_strlen($message, $encoding)) <= $length) {
            return $message;
        }

        $firstCut = $lengthInBytes ?
            mb_strcut($message, 0, $length - strlen($cap), $encoding) :
            mb_substr($message, 0, $length - mb_strlen($cap, $encoding), $encoding);

        $lastDelimiter = mb_strrpos($firstCut, $delimiter, $encoding);

        return mb_substr($firstCut, 0, $removeLastDelimiter ? $lastDelimiter : $lastDelimiter + mb_strlen($delimiter, $encoding)) . $cap;
    }