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memory – How to download large files through PHP script

Posted by: admin April 23, 2020 Leave a comment

Questions:

Using PHP, I am trying to serve large files (up to possibly 200MB) which aren’t in a web accessible directory due to authorization issues. Currently, I use a readfile() call along with some headers to serve the file, but it seems that PHP is loading it into memory before sending it. I intend to deploy on a shared hosting server, which won’t allow me to use much memory or add my own Apache modules such as X-Sendfile.

I can’t let my files be in a web accessible directory for security reasons. Does anybody know a method that is less memory intensive which I could deploy on a shared hosting server?

EDIT:

if(/* My authorization here */) {
        $path = "/uploads/";
        $name = $row[0];           //This is a MySQL reference with the filename
        $fullname = $path . $name; //Create filename
        $fd = fopen($fullname, "rb");
        if ($fd) {
            $fsize = filesize($fullname);
            $path_parts = pathinfo($fullname);
            $ext = strtolower($path_parts["extension"]);
            switch ($ext) {
                case "pdf":
                header("Content-type: application/pdf");
                break;
                case "zip":
                header("Content-type: application/zip");
                break;
                default:
                header("Content-type: application/octet-stream");
                break;
            }
            header("Content-Disposition: attachment; filename=\"".$path_parts["basename"]."\"");
            header("Content-length: $fsize");
            header("Cache-control: private"); //use this to open files directly
            while(!feof($fd)) {
                $buffer = fread($fd, 1*(1024*1024));
                echo $buffer;
                ob_flush();
                flush();    //These two flush commands seem to have helped with performance
            }
        }
        else {
            echo "Error opening file";
        }
        fclose($fd);
How to&Answers:

If you use fopen and fread instead of readfile, that should solve your problem.

There’s a solution in the PHP’s readfile documentation showing how to use fread to do what you want.

Answer:

To download large files from server, I have changed the below settings in php.ini file:

Upload_max_filesize  - 1500 M
Max_input_time  - 1000
Memory_limit    - 640M
Max_execution_time -  1800
Post_max_size - 2000 M

Now, I am able to upload and download 175MB video on server.
Since, I have the dedicated server. So, making these changes were easy.

Below is the PHP script to download the file. I have no made any changes in this code snippet for large file size.

// Begin writing headers

            ob_clean(); // Clear any previously written headers in the output buffer

            if($filetype=='application/zip')
            {
                if(ini_get('zlib.output_compression'))
                    ini_set('zlib.output_compression', 'Off');
                $fp = @fopen($filepath, 'rb'); 
                if (strstr($_SERVER['HTTP_USER_AGENT'], "MSIE"))
                {
                    header('Content-Type: "$content_type"');
                    header('Content-Disposition: attachment; filename="'.$filename.'"');
                    header('Expires: 0');
                    header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
                    header("Content-Transfer-Encoding: binary");
                    header('Pragma: public');
                    header("Content-Length: ".filesize(trim($filepath)));
                }
                else
                {
                    header('Content-Type: "$content_type"');
                    header('Content-Disposition: attachment; filename="'.$filename.'"');
                    header("Content-Transfer-Encoding: binary");
                    header('Expires: 0');
                    header('Pragma: no-cache');
                    header("Content-Length: ".filesize(trim($filepath)));
                }

                fpassthru($fp);
                fclose($fp);
            }
            elseif($filetype=='audio'|| $filetype=='video')
            { 
                global $mosConfig_absolute_path,$my;
                ob_clean();
                header("Pragma: public");
                header('Expires: 0');
                header('Cache-Control: no-store, no-cache, must-revalidate');
                header('Cache-Control: pre-check=0, post-check=0, max-age=0');
                header("Cache-Control: public");    
                header("Content-Description: File Transfer");
                header("Content-Type: application/force-download"); 
                header("Content-Type: $content_type");
                header("Content-Length: ".filesize(trim($filepath)));
                header("Content-Disposition: attachment; filename=\"$filename\"");
                // Force the download           
                header("Content-Transfer-Encoding: binary");            
                @readfile($filepath);
            }
              else{ // for all other types of files except zip,audio/video
                ob_clean();
                header("Pragma: public");
                header('Expires: 0');
                header('Cache-Control: no-store, no-cache, must-revalidate');
                header('Cache-Control: pre-check=0, post-check=0, max-age=0');
                header("Cache-Control: public");    
                header("Content-Description: File Transfer");
                header("Content-Type: $content_type");
                header("Content-Length: ".filesize(trim($filepath)));
                header("Content-Disposition: attachment; filename=\"$filename\"");
                // Force the download           
                header("Content-Transfer-Encoding: binary");            
                @readfile($filepath);       
            }
            exit;

Answer:

If you care about performance, there is xsendfile, available in apache, nginx and lighttpd as module. Check the readfile() doc’s users comments.

There are also modules for these webservers which accept a url with an additional hash value which allows downloading the file for a short time period. This can be also used to solve authorization issues.

Answer:

You could also handle this in the style of the Gordian Knot – that is to say, sidestep the problem entirely. Keep the files in a non-accessible directory, and when a download is initiated you can simply

tempstring = rand();
symlink('/filestore/filename.extension', '/www/downloads'.tempstring.'-filename.extension');
echo("Your download is available here: <a href='/downloads/'.tempstring.'-filename.extension');

and setup a cronjob to unlink() any download links older than 10 minutes. Virtually no processing of your data is required, no massaging of HTTP headers, etc.

There are even a couple libraries out there for just this purpose.