保留json字符串中文的函数，代替json_encode

// 格式化json中的汉字函数
    protected function encode_json($str) {
        $strs = urldecode(json_encode($this->url_encode($str)));
        return $strs;
    }
    protected function url_encode($str) {
        if(is_array($str)) {
            foreach($str as $key=>$value) {
                $str[urlencode($key)] = $this->url_encode($value);
            }
        } else {
            $str = urlencode($str);
        }
        return $str;
    }