How to download files safely with PHP_php tips

<&#63;php
header('Content-Type:text/html;Charset=utf-8');
define('ROOT_PATH', dirname(__FILE__));
/**
 * 下载文件
 * @param string $file_path 绝对路径
 */
function downFile($file_path) {
  //判断文件是否存在
  $file_path = iconv('utf-8', 'gb2312', $file_path); //对可能出现的中文名称进行转码
  if (!file_exists($file_path)) {
    exit('文件不存在！');
  }
  $file_name = basename($file_path); //获取文件名称
  $file_size = filesize($file_path); //获取文件大小
  $fp = fopen($file_path, 'r'); //以只读的方式打开文件
  header("Content-type: application/octet-stream");
  header("Accept-Ranges: bytes");
  header("Accept-Length: {$file_size}");
  header("Content-Disposition: attachment;filename={$file_name}");
  $buffer = 1024;
  $file_count = 0;
  //判断文件是否结束
  while (!feof($fp) && ($file_size-$file_count>0)) {
    $file_data = fread($fp, $buffer);
    $file_count += $buffer;
    echo $file_data;
  }
  fclose($fp); //关闭文件
}
downFile(ROOT_PATH . '/down/Sunset.jpg');
&#63;>