Prevent multiple connections while file download in php - php

Question

There is a PHP function download() that allows user to download the file. The decrypted file is created on server and provided to user using readfile($file) . But when Internet Download Manager downloads it using multiple connections, it makes multiple connections and that file is created multiple times on the server, one for each connection. What could be the best possible solution to create only one file for single user, even when there are multiple requests for download. And after download the should be deleted also.
Following is the sample code for download.
public function download($new_filename,$original_filename){
$fp2=fopen($new_filename,'wb'); //create empty file name $new_filename
fputs($fp2,base64_decode(file_get_contents($original_filename)));//decoding and writing to $fp2
header('Content-Description: File Transfer');
header("Content-Type: application/".$ext);
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
header('Content-Disposition: attachment; filename="' . $new_filename . '"');
header("Content-Length: " . filesize($new_filename));
ob_clean();
flush();
readfile($new_filename);
/***** removing temporary decoded file ****/
if(file_exists($new_filename)) {
chmod($new_filename,0777); //Change the file permissions if allowed read and write and execute
unlink($new_filename); //remove the file
}
fclose($fp2);
}

Answer 1

I guess the easiest way to accomplish what you want is something like this:
Generate unique download urls with a "ticket" that gives one time access to the file (eg. dl.php?file=ABC123&ticket=1231292), store this ticket in a database or some other structure when you generate it, so that you can invalidate it when the download begins.
In your download script you check if the ticketid is valid, if not you respond with a 403 HTTP status.
If it is valid then begin generating the file etc., invalidate the ticket and then start to send the file to the client.

Answer 2

Maybe you can use base64_decode and file_get_contents instead of readfile like:
public function download($new_filename,$original_filename) {
header('Content-Description: File Transfer');
header("Content-Type: application/".$ext);
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
header('Content-Disposition: attachment; filename="' . $new_filename . '"');
header("Content-Length: " . filesize(base64_decode(file_get_contents($original_filename))));
echo base64_decode(file_get_contents($original_filename));
}
And you can add something to lock 1 connection by ip address using $_SERVER['REMOTE_ADDR']