[5.6] Add stream download response

[TheoKouzelis]

Adds the ability to respond with remote files as downloads.

<?php

    Route::get('/', function () {
        return response()->streamDownload(function () {
            echo file_get_contents('https://my.remote.com/file/store-12345.jpg');
        }, 'nice-name.jpg');
    });

[m1guelpf]

For reference, this is a resubmission of #22764 to 5.6

[taylorotwell]

Is anything actually being streamed here? Doesn't file_get_contents load the content of the entire remote URL into memory?

[m1guelpf]

@taylorotwell The file_get_contents above is an example, the important thing is that this PR allows developers to return anything the callable returns as an attachament.

Imagine I'm using the GitHub API to get the readme of this repo. Now I can "stream" the file from memory instead of saving it to a file and returning the file:

<?php

    Route::get('/', function () {
        return response()->streamDownload(function () {
            echo GitHub::api('repo')->contents()->readme('laravel', 'laravel')['contents']
        }, 'laravel-readme.md');
    });

[TheoKouzelis]

Hi @taylorotwell

Thanks for the PR review.

Yeah @m1guelpf has explained the PR perfectly. Just to add a little more context, this PR was born out of this Stackoverflow question where people were looking to use the "download" response with remote files and I thought the "stream" response would be the best way to achieve that.

@m1guelpf You could be right about the return instead of echo. But I can only find examples of the StreamResponse closures having files echoed in them. Example 1 Example 2

[m1guelpf]

@TheoKouzelis Yeah, you're rigth. It makes sense, you have to use echo.

[joecohens]

Not sure if this helps, but we can also see this case on the League Glide Symfony response which is also used by the Glide Laravel integration:

https://github.com/thephpleague/glide-symfony/blob/2dc271c959aa86c060261e2a93c493a54f98efbb/src/Responses/SymfonyResponseFactory.php#L26-L57

Note: If I'm not mistaken, also the dev should know how to write the streamed response closure, like for example when using file_get_contents:

https://github.com/twistor/flysystem-http/blob/acba993b790777067d7aa405458b4e06d329a9f3/src/HttpAdapter.php#L174-L187

Hope it helps 😄

[TheoKouzelis]

Thanks for merging the PR @taylorotwell

If we don't include the contract change. Would it be worth me back porting this to the other 5.x branches?

[CharifMakaoui]

Is this method works for large files, like hd movies (1080p)