万能文字截取

$string1 = "你是我的上帝上帝上帝上帝上帝";

function cut_str($string, $sublen, $start = 0, $charset = 'UTF-8') {
    if ($charset == 'UTF-8') {
        $pa = "/[x01-x7f]|[xc2-xdf][x80-xbf]|xe0[xa0-xbf][x80-xbf]|[xe1-xef][x80-xbf][x80-xbf]|xf0[x90-xbf][x80-xbf][x80-xbf]|[xf1-xf7][x80-xbf][x80-xbf][x80-xbf]/";
        preg_match_all($pa, $string, $t_string);

        if (count($t_string[0]) - $start > $sublen)
            return join('', array_slice($t_string[0], $start, $sublen)) . "...";
        return join('', array_slice($t_string[0], $start, $sublen));
    }
    else {
        $start = $start * 2;
        $sublen = $sublen * 2;
        $strlen = strlen($string);
        $tmpstr = '';

        for ($i = 0; $i < $strlen; $i++) {
            if ($i >= $start && $i < ($start + $sublen)) {
                if (ord(substr($string, $i, 1)) > 129) {
                    $tmpstr.= substr($string, $i, 2);
                } else {
                    $tmpstr.= substr($string, $i, 1);
                }
            }
            if (ord(substr($string, $i, 1)) > 129)
                $i++;
        }
        if (strlen($tmpstr) < $strlen)
            $tmpstr.= "...";
        return $tmpstr;
    }
}

echo cut_str($string1, 10);