Stream a PDF file in Laravel 5.2 - php

Question

Hi everyone! I'm working on a Laravel 5.2 application in which the user can download a variety of files. One of these is a 'User guide', explaining how the website is set up and functionalities etc. I would like the PDF to be streamed in another page, so that the user is still within the application. The controller which I am using is:
public function userguidePDF(){
return response()->stream('../public/download/userguide.pdf');
}
But this returns:
Argument 1 passed to
Symfony\Component\HttpFoundation\StreamedResponse::__construct() must
be callable, string given, called in
/path/to/laravel/vendor/laravel/framework/src/Illuminate/Routing/ResponseFactory.php
on line 117 and defined
I have searched on the internet for a method, which leaded me to the following syntax:
return response()->stream($callback, 200, $headers);
Unfortunately, I am unable to find more documentation on the parameters because I don't understand them. Could someone please explain to me what the $callback, 200, $header are as parameters and how I can use this?

Answer 1

https://laravel.com/docs/5.2/responses#view-responses
public function userguidePDF() {
return response()->file(
public_path('download/userguide.pdf')
);
}

Answer 2

$callback should be a function that ouputs your PDF. For example:
$callback = function()
{
$handle = fopen("../public/download/userguide.pdf", "r");
$filecontent= fread($handle, filesize("../public/download/userguide.pdf"));
fclose($handle);
return $filecontent;
};

Answer 3

You can use download also
return Response::download($file, 'filename.pdf', $headers);
here is the documentation for streaming and also downlaod.
https://laravel.com/api/5.2/Illuminate/Routing/ResponseFactory.html#method_stream
EDIT
Use headers like this
// We'll be outputting a PDF
header('Content-Type: application/pdf');
// It will be called downloaded.pdf
header('Content-Disposition: attachment; filename="downloaded.pdf"');