(PHP) Problem with filename after downloading it - php

Question

While writing a PHP-Script, im stuck at an issue i cant resolve.
The PHP-Script consist in letting a user download a .mp4 file. The download works without any issues but the file downloaded can not be played.
Heres the code:
<?php
$filepath = "/www/servermedia/technounion.mp4";
$filename = basename($filepath);
header("Content-type: video/mp4");
header("Content-Disposition: attachment; filename=.$filename");
readfile($filename);
exit;
?>
After the .mp4 file gets downloaded, it cannot be played.
It looks like this:
The error message means that Windows Media Player cannot play back the file because probably the player doesnt support the codec. I already tried with VLC but it does not work either.
EDIT:
Comparing both file sizes, the downloaded file is only a couple bytes large instead of the 3,73 MB of the file on the server

Answer 1

Your code is not well-formed, you miss to escape double-quotes by adding single-quotes as I done here, please test my answer.
<?php
$filepath = "/www/servermedia/technounion.mp4";
$filename = basename($filepath);
header('Content-Type: video/mp4');
header('Content-Disposition: attachment; filename="' . $filename . '"');
readfile($filename);
exit;
?>
But I suggest a more complex way:
<?php
$filepath = $_SERVER['DOCUMENT_ROOT'] . "/www/servermedia/technounion.mp4";
$filename = basename($filepath);
header('Content-Type: video/mp4');
header('Content-Disposition: attachment; filename="' . $filename . '"');
header('Content-Transfer-Encoding: binary');
header('Connection: Keep-Alive');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
header('Content-Length: ' . sprintf("%u", filesize($filepath)));
set_time_limit(0);
$fh = fopen($filepath, "rb");
while (!feof($fh)) {
echo fgets($fh);
ob_flush();
flush();
}
fclose($fh);
exit;
?>
$_SERVER['DOCUMENT_ROOT'] is useful to get the full path from the server
set_time_limit(0) is useful to avoid any timeout during download
fgets() is useful for reading large files
ob_flush() and flush() assure that there is not other output in the buffer
I hope this helps.

Answer 2

Is the downloaded file the exact same filesize?
Does the content type exist in your webserver?
header("Content-Type: video/mp4"); Note capital 'T' for type.
This maybe worth testing with to see you can serve the file content inline:
http://www.phpmind.com/blog/2016/10/how-to-use-php-to-output-an-mp4-video/