php 文件下载 与 上传

public function download(){

     $url = Env::get('ROOT_PATH').'/public/uploads/xfile/a.xlsx';

    if(file_exists($url))
    {
        $this->downloads($url,'a.xlsx');
    }else{
       exit('400');
    }

}

public function downloads($file_url,$file_name=''){

    if(!isset($file_url)||trim($file_url)==''){
        echo '500';
    }
    if(!file_exists($file_url)){ //检查文件是否存在
        echo '404';
    }

    $file_size= filesize($file_url);
    ob_clean();
    header('Pragma: public');
    header('Last-Modified:'.gmdate('D, d M Y H:i:s') . 'GMT');
    header('Cache-Control:no-store, no-cache, must-revalidate');
    header('Cache-Control:pre-check=0, post-check=0, max-age=0');
    header('Content-Transfer-Encoding:binary');
    header('Content-Encoding:none');
    header('Content-type:multipart/form-data');
    header('Content-Disposition:attachment; filename="'.$file_name.'"'); //设置下载的默认文件名
    header('Content-length:'. $file_size);
    $fp = fopen($file_url, 'r');
    while(connection_status() == 0 && $buf = @fread($fp, 819200)){
        echo $buf;
    }
    fclose($fp);
    @unlink($file_size);
    @flush();
    @ob_flush();
    exit();
}