mb_strimlen.php

<?php
function mb_strimlen($str, $start, $length, $trimmarker = '', $encoding = false) {
    $encoding = $encoding ? $encoding : mb_internal_encoding();
    $str = mb_substr($str, $start, mb_strlen($str), $encoding);
    if (mb_strlen($str, $encoding) > $length) {
        $markerlen = mb_strlen($trimmarker, $encoding);
        $str = mb_substr($str, 0, $length - $markerlen, $encoding) . $trimmarker;
    }
    return $str;
}