Getting file size from S3 download - php

Question

So I have files stored on Amazon S3. My customers download these files from our website, they click download and it sends the info to our download.php page (the customers don't see this page), but there it uses PHP to get the file name and path (code below). But the issue we have is that it's not telling the browser the file size, so when the customer is downloading they see "remaining time unknown". How can I make it so that the download.php page can get that information and pass it alone?
<?php
$file_path = "http://subliminalsuccess.s3.amazonaws.com/";
$file_name = $_GET['download'];
$file = file_get_contents('$file_name');
header('application/force-download');
header( 'Content-Type: application/octet-stream' );
header('Content-Disposition: attachment; filename="'.$file_name.'"');
$pos = strpos($file_name, "http");
if ($pos !== false && $pos == 0)
{
readfile($file_name);
} else readfile($file_path.$file_name);
?>

Answer 1

That's very easy. Look, when you do file_get_contents(), you can get your file size with strlen(). Then you send Content-Length header in the response.
<?php
$file_path = 'http://subliminalsuccess.s3.amazonaws.com/';
$file = trim($_GET['download']);
$file_name = $file_path.$file;
$file_contents = file_get_contents($file_name)
OR die('Cannot get the file: '.$file);
header('Content-Type: application/force-download');
header('Content-Type: application/octet-stream');
header('Content-Length: '.strlen($file_contents));
header('Content-Disposition: attachment; filename="'.basename($file).'"');
echo $file;
BTW, there're so many mistakes in your code. For example, you read files twice, one time with file_get_contents() and second time with readfile(). $file_name variable doesn't have URI. file_get_contents('$file_name') is also wrong.
Also, you don't check your incoming URLs, but just readfile() it which is not nice as someone might pass any URLs to your script...