[php] Force file download with php using header()

I want the user to be able to download some files I have on my server, but when I try to use any of the many examples of this around the internet nothing seems to work for me. I've tried code like this:

<?php

$size = filesize("Image.png");

header('Content-Description: File Transfer');
header('Content-Type: image/png');
header('Content-Disposition: attachment; filename="Image.png"');
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
header('Content-Length: ' . $size);
readfile("Image.png");

I've even tried to use the most basic example I could find, like this:

<?php
header('Content-type: image/png');
header('Content-Disposition: attachment; filename="Image.png"');
readfile('Image.png');

When I've tested this I have removed all the other code I have and used an empty file with just this code to remove any faults created by external sources.

When I look in the console the file gets sent with the right headers i.e

'Content-Disposition: attachment; filename="Image.png"'

But the save dialog isn't displayed.

I've also tried with inline instead of attachment in the content disposition header but that didn't make a difference either, I've tested this in Firefox 8.0.1 Chrome 15.0.874.121 and Safari 5.1.1.

I’m pretty sure you don’t add the mime type as a JPEG on file downloads:

header('Content-Type: image/png');

These headers have never failed me:

$quoted = sprintf('"%s"', addcslashes(basename($file), '"\\'));
$size   = filesize($file);

header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename=' . $quoted); 
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: ' . $size);

This worked for me like a charm for downloading PNG and PDF.

header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="'.$file_name.'"');
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
header('Content-Length: ' . filesize($file_url)); //Absolute URL
ob_clean();
flush();
readfile($file_url); //Absolute URL
exit();

the htaccess solution

<filesmatch "\.(?i:doc|odf|pdf|cer|txt)$">
  Header set Content-Disposition attachment
</FilesMatch>

you can read this page: https://www.techmesto.com/force-files-to-download-using-htaccess/

Based on Farhan Sahibole's answer:

        header('Content-Disposition: attachment; filename=Image.png');
        header('Content-Type: application/octet-stream'); // Downloading on Android might fail without this
        ob_clean();

        readfile($file);

This is all I needed for this to work. I stripped off anything that isn't required for this to work.

Key is to use ob_clean();

Here is a snippet from me in testing... obviously passing via get to the script may not be the best... should post or just send an id and grab guid from db... anyhow.. this worked. I take the URL and convert it to a path.

// Initialize a file URL to the variable
$file = $_GET['url'];
$file = str_replace(Polepluginforrvms_Plugin::$install_url, $DOC_ROOT.'/pole-permitter/', $file );

$quoted = sprintf('"%s"', addcslashes(basename($file), '"\\'));
$size   = filesize($file);

header( "Content-type: application/octet-stream" );
header( "Content-Disposition: attachment; filename={$quoted}" );
header( "Content-length: " . $size );
header( "Pragma: no-cache" );
header( "Expires: 0" );
readfile( "{$file}" );

its work for me

$attachment_location = "filePath";
if (file_exists($attachment_location)) {

    header($_SERVER["SERVER_PROTOCOL"] . " 200 OK");
    header("Cache-Control: public"); // needed for internet explorer
    header("Content-Type: application/zip");
    header("Content-Transfer-Encoding: Binary");
    header("Content-Length:".filesize($attachment_location));
    header("Content-Disposition: attachment; filename=filePath");
    readfile($attachment_location);
    die();
} else {
    die("Error: File not found.");
}