PHP截取中英文混合防止乱码

 function utf8_substr($str, $from, $len = 180, $suffix = '') { 
        $str     = trim($str);
        $str     = strip_tags($str);
        $pre_len = strlen($str);
        $str     = preg_replace('#^(?:[\x00-\x7F]|[\xC0-\xFF][\x80-\xBF]+){0,'. $from .'}'.'((?:[\x00-\x7F]|[\xC0-\xFF][\x80-\xBF]+){0,'. $len .'}).*#s', '$1', $str);
        if ($pre_len != strlen($str)) {
            $str .= $suffix;
        }
        return $str;
    }