PHP & MYSQL blank result. Script suddenly stops. No errorlog - php

Question

I want to wrtite a simple code that lets me download a file depending on the ID specified in the URL. For doing that, it connects to the database and tries to get the information of the file associated to the ID. Then, it sends the headers with the extracted info and the file.
But for reasons that I don't know, it outputs a blank page. There aren't any logfiles anywhere, just it suddenly stops.
Please, a bit of help would be really appreciated. Thanks you for spending your time
<?php
//We include the variables needed to do the connection to the db
include '../php/vars.php';
$id=$_GET['id'];
//We connect to the database
$con = mysql_connect("$dbsv","$dbuser","$dbpass");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
mysql_select_db("$dbname", $con);
// We do the query
if ($query === false) {echo mysql_error();}
$query = "SELECT name,filetype FROM links WHERE id=$id";
$result = mysql_query($query);
// Check result. This shows the actual query sent to MySQL, and the error. Useful for debugging.
if (!$result) {
$message = 'Invalid query: ' . mysql_error() . "\n";
$message .= 'Whole query: ' . $query;
die($message);
}
while ($row = mysql_fetch_assoc($result))
{
// Assign variables
$filename = $row['name'];
$type = $row['filetype'];
}
//We download the file
if (file_exists($filename)) {
header('Content-Description: File Transfer');
header( "Content-type: $type");
header('Content-Disposition: attachment; filename='.basename($filename));
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . filesize($filename));
fopen("$filename", "r");;
exit;
}
?>
I'm not native English. Expect gramatical, syntax and ortographical errors. If you detect them, please, notify me.

Answer 1

As I see you want to pass the file right?
fopen("$filename", "r");
replace this with
readfile($filename);
fopen just opens a file pointer and does absolutly nothing with the file itself, you have to use fread, write and fclose to do stuff with the file, there are more operations but basicly fopen just gives you a file pointer

Answer 2

There are a lot of logical errors, you need to fix:
if ($query === false) {echo mysql_error();}
$query is not set at this point. so it's never false. (You are saying basically if (null === false))
while ($row = mysql_fetch_assoc($result))
{
// Assign variables
$filename = $row['name'];
$type = $row['filetype'];
}
//We download the file
if (file_exists($filename)) {
Depending on your result count you are overriding $filename multiple times - and then only perform an operation on the LAST value.
Either move the logic into the while loop.
Or don't use a while-loop if you are expecting a single result.
Then:
fopen("$filename", "r");
You are opening a file - and then? doing nothing at all. Continue with fread() until EOF is reached and then use fclose($handle) bevor outputting the result.
(This is the reason for simply seeing nothing)

Answer 3

You would use readfile() instead. readfile() reads a file and writes it to the output buffer.
Here is manual link http://php.net/manual/en/function.readfile.php
if (file_exists($filename)) {
header('Content-Description: File Transfer');
header( "Content-type: $type");
header('Content-Disposition: attachment; filename='.basename($filename));
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . filesize($filename));
readfile($filename);
exit;
}