Solution to garbled Chinese characters in PHP downloads

$file_name = iconv("utf-8","gb2312",$file_name);

public function downloadAction(){
        header("Content-type:text/html;charset=utf-8");
        // 文件名
        $file_name="中文.txt";
        //用以解决中文不能显示出来的问题
        $file_name = iconv("utf-8","gb2312",$file_name);
        // 文件路径
        // $file_sub_path=$_SERVER['DOCUMENT_ROOT'];
        $file_path=$file_sub_path.'/'.$file_name;
        //首先要判断给定的文件存在与否
        if( !file_exists($file_path) || $file_path=='/' ){
            $arr = array(
'code' => '-103',
'message' => '操作失败',
'data' => '没有该文件文件'
 );
            echo json_encode( $arr );
            die();
        }
        $fp=fopen($file_path,"r");
        $file_size=filesize($file_path);
        //下载文件需要用到的头
        Header("Content-type: application/octet-stream");
        Header("Accept-Ranges: bytes");
        Header("Accept-Length:".$file_size);
        Header("Content-Disposition: attachment; filename=".$file_name);
        $buffer=1024;
        $file_count=0;
        //向浏览器返回数据
        while(!feof($fp) && $file_count<$file_size){
            $file_con=fread($fp,$buffer);
            $file_count+=$buffer;
            echo $file_con;
        }
        fclose($fp);
        die();
    }