[PHP] 中文字符串截取(UTF8与非UTF8)

来源：http://zhidao.baidu.com/question/282309749.html

function cutstr ($string, $length, $dot = '...', $charset = 'utf-8') {

    //功能:按长度截取字符串
    //$string, $length, $dot,$charset
    //字符串,要取长度,截断符,编码


    if (strlen($string) <= $length) {
        return $string;
    }

    $string = str_replace(array('&', '"', '<', '>'), array('&', '"', '<', '>'), $string);

    $strcut = '';
    if (strtolower($charset) == 'utf-8') {

        $n = $tn = $noc = 0;
        while ($n < strlen($string)) {

            $t = ord($string[$n]);
            if ($t == 9 || $t == 10 || (32 <= $t && $t <= 126)) {
                $tn = 1;
                $n++;
                $noc++;
            } elseif (194 <= $t && $t <= 223) {
                $tn = 2;
                $n += 2;
                $noc += 2;
            } elseif (224 <= $t && $t <= 239) {
                $tn = 3;
                $n += 3;
                $noc += 2;
            } elseif (240 <= $t && $t <= 247) {
                $tn = 4;
                $n += 4;
                $noc += 2;
            } elseif (248 <= $t && $t <= 251) {
                $tn = 5;
                $n += 5;
                $noc += 2;
            } elseif ($t == 252 || $t == 253) {
                $tn = 6;
                $n += 6;
                $noc += 2;
            } else {
                $n++;
            }

            if ($noc >= $length) {
                break;
            }
        }
        if ($noc > $length) {
            $n -= $tn;
        }
        $strcut = substr($string, 0, $n);

    } else {
        for ($i = 0; $i < $length; $i++) {
            $strcut .= ord($string[$i]) > 127 ? $string[$i] . $string[++ $i] : $string[$i];
        }
    }
    $strcut = str_replace(array('&', '"', '<', '>'), array('&', '"', '<', '>'), $strcut);

    return $strcut . $dot;
}



$str = "我们要截取的字符串";
echo cutstr($str, 15, "...", 'utf-8');