<?php
function smartDetectUTF8($string)
{
    static $result = array();
    if(! array_key_exists($key = md5($string), $result))
    {
        $utf8 = "
            /^(?:
                [\x09\x0A\x0D\x20-\x7E]                            # ASCII
                | [\xC2-\xDF][\x80-\xBF]                             # non-overlong 2-byte
                | \xE0[\xA0-\xBF][\x80-\xBF]                       # excluding overlongs
                | [\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}           # straight 3-byte
                | \xED[\x80-\x9F][\x80-\xBF]                      # excluding surrogates
                | \xF0[\x90-\xBF][\x80-\xBF]{2}                 # planes 1-3
                | [\xF1-\xF3][\x80-\xBF]{3}                          # planes 4-15
                | \xF4[\x80-\x8F][\x80-\xBF]{2}                  # plane 16
            )+$/xs
        ";
        $result[$key] = preg_match(trim($utf8), $string);
    }
    return $result[$key];
}
function smartStrlen($string)
{
    $result = 0;
    $number = smartDetectUTF8($string) ? 3 : 2;
    for($i = 0; $i < strlen($string); $i += $bytes)
    {
        $bytes = ord(substr($string, $i, 1)) > 127 ? $number : 1;
        $result += $bytes > 1 ? 1.0 : 0.5;
    }
    return $result;
}
function smartSubstr($string, $start, $length = null)
{
    $result = '''';
    $number = smartDetectUTF8($string) ? 3 : 2;
    if($start < 0)
    {
        $start = max(smartStrlen($string) + $start, 0);
    }
    for($i = 0; $i < strlen($string); $i += $bytes)
    {
        if($start <= 0)
        {
            break;
        }
        $bytes = ord(substr($string, $i, 1)) > 127 ? $number : 1;
        $start -= $bytes > 1 ? 1.0 : 0.5;
    }
    if(is_null($length))
    {
        $result = substr($string, $i);
    }
    else
    {
        for($j = $i; $j < strlen($string); $j += $bytes)
        {
            if($length <= 0)
            {
                break;
            }
            if(($bytes = ord(substr($string, $j, 1)) > 127 ? $number : 1) > 1)
            {
                if($length < 1.0)
                {
                    break;
                }
                $result .= substr($string, $j, $bytes);
                $length -= 1.0;
            }
            else
            {
                $result .= substr($string, $j, 1);
                $length -= 0.5;
            }
        }
    }
    return $result;
}
function smarty_modifier_smartTruncate($string, $length = 80, $etc = ''...'',
                                       $break_words = false, $middle = false)
{
    if ($length == 0)
        return '''';
    if (smartStrlen($string) > $length) {
        $length -= smartStrlen($etc);
        if (!$break_words && !$middle) {
            $string = preg_replace(''/\s+?(\S+)?$/'', '''', smartSubstr($string, 0, $length+1));
        }
        if(!$middle) {
            return smartSubstr($string, 0, $length).$etc;
        } else {
            return smartSubstr($string, 0, $length/2) . $etc . smartSubstr($string, -$length/2);
        }
    } else {
        return $string;
    }
}
?>

{$content|smartTruncate:5:".."}（$content等于"A中B華C人D民E共F和G國(guó)H"）