Changing CRC of a file through readfile() - php

Question

I have this code set up that lets a user download a file through my server from a URL they specify. The file streams through using readfile() so it only uses my bandwidth.
<?php
set_time_limit(0);
$urlParts = explode("/", $_SERVER['PHP_SELF']);
$file = $urlParts[3];
header("Cache-Control: public, must-revalidate");
header("Pragma: hack");
header("Content-Type: application/force-download");
header('Content-Disposition: attachment; filename=' . $file);
header("Content-Transfer-Encoding: binary\n");
readfile($file);
?>
This script works, but it does not change the CRC hash of the downloaded file. What I want it to do is append some random bits to the end of the file so it can change the hash without corrupting it. I have tried adding something like echo md5(rand() . time()); to the end of the script but it doesn't work.
If this is possible with something like cURL I'd appreciate if someone could put up some code samples, because i'd switch to cURL if this was possible.
Thanks for your help.

Answer 1

Hmm, your code works for me:
test.php:
set_time_limit(0);
$urlParts = explode("/", $_SERVER['PHP_SELF']);
//$file = $urlParts[3];
$file = 'toread.txt';
header("Cache-Control: public, must-revalidate");
header("Pragma: hack");
header("Content-Type: application/force-download");
header('Content-Disposition: attachment; filename=' . $file);
header("Content-Transfer-Encoding: binary\n");
readfile($file);
echo md5(rand() . time());
?>
toread.txt:
This is the content of toread.txt
Now using curl, I get the following results:
>curl -i http://example.com/test.php
HTTP/1.1 200 OK
Date: Tue, 04 Mar 2014 07:09:39 GMT
Server: Apache
Cache-Control: public, must-revalidate
Pragma: hack
Content-Disposition: attachment; filename=toread.txt
Content-Transfer-Encoding: binary
Transfer-Encoding: chunked
Content-Type: application/force-download
Proxy-Connection: Keep-Alive
Connection: Keep-Alive
Age: 0
This is the content of toread.txt38d8a8009fad7315bdf5e823a06018e7
And the second one:
>curl -i http://example.com/test.php
HTTP/1.1 200 OK
Date: Tue, 04 Mar 2014 07:09:57 GMT
Server: Apache
Cache-Control: public, must-revalidate
Pragma: hack
Content-Disposition: attachment; filename=toread.txt
Content-Transfer-Encoding: binary
Transfer-Encoding: chunked
Content-Type: application/force-download
Proxy-Connection: Keep-Alive
Connection: Keep-Alive
Age: 0
This is the content of toread.txt3b87356ea9ee007b70cfd619e31da950