php实现文件下载的一段代码

<script>ec(2);</script>

$file_dir=$totalDirectory;
     $file_name=$filename;
     //echo ''./db/''.$file_dir.$file_name;
    if (file_exists($file_dir.$file_name)){
          $file=fopen($file_dir.$file_name,''r'');
         Header(''Content-type:application/octet-stream'');
         Header(''Accept-Ranges:bytes'');
         Header(''Content-Disposition:attachment;filename=''.$file_name);
         echo fread($file,filesize($file_dir.$file_name));
         fclose($file);
         exit;
        
     }else{
         echo ''file is not exists'';
     }