The Weebly Engineering blog has a new tutorial posted about streamed file zipping and downloading in a PHP based application. This allows the download to start even while the file is being compressed into a zip archive on the backend.

Did you notice that on Dropbox.com, you can select a folder and start downloading it while it’s being zipped? This on-the-fly zipping feature comes handy for both the user and the server?—?as a user you don’t have to wait until the files are zipped on the back end before the downloading starts, and it saves the server from creating a temporary zip file and deleting it afterwards.

[...] To implement this feature with PHP, we handle the zipping and streaming work on the back end using ZipStream. Assuming your files are on the server and can be loaded with file_get_contents given a path.

They include some of the details of the HTTP request format for the stream (as an attachment type) and how you can use the ZipStream package to quickly implement it into your code. They include a simple example of implementing it in a form, allowing the user to easily integrate it and work around some of the browser based security controls.