PHP zip file class

I'm working on a Drupal module (can't say what) that needs to create a archive. I landed on ZIP, because it's the easiest to implement without requiring any external libs.
I searched around and found this, and with a few improvements I ended up with this: http://xqus.com/tools/class.zipfile.phps

The following changes were made:

• Changed the name of the output method to save
• Added some error checking in the save method
• Made the save method return boolean
• Added a check to see if the $files param to addFiles in an array
• Changed the way the addFiles method reads file contents
• Made the addFiles method return boolean
• Made a output method to output the zipfile directly to the browser