Rob Allen has a new post to his site today showing you how to create a ZIP file with the help of PHP's ZipArchive functionality. The latest versions would need to be installed as an extension (PECL) if they're not already there, but it makes creating the archives a lot simpler.
I recently had a requirement to create a zip file from a number of files created within my application. As it has been years since I last had this problem, I had a look around and discovered that PHP 5.2 has the ZipArchive class that makes this easy. ZipArchive is fully featured, but as I just wanted to create a simple zip file.
All it requires is a few short lines of code - one to open the archive itself, some to add in the files to compress down and another to close and create the file. It's a pretty simple process using this handy extension. Rob also included a bit of sample code showing how to send it out for download with the correct headers.