UTF-8 문자열 자르기

function strcut_utf8($str, $len, $checkmb=false, $tail='...') {
    preg_match_all('/[\xEA-\xED][\x80-\xFF]{2}|./', $str, $match);

    $m    = $match[0];
    $slen = strlen($str);  // length of source string
    $tlen = strlen($tail); // length of tail string
    $mlen = count($m); // length of matched characters

    if ($slen <= $len) return $str;
    if (!$checkmb && $mlen <= $len) return $str;

    $ret   = array();
    $count = 0;

    for ($i=0; $i < $len; $i++) {
        $count += ($checkmb && strlen($m[$i]) > 1)?2:1;
        if ($count + $tlen > $len) break;
        $ret[] = $m[$i];
    }

    return join('', $ret).$tail;
}