PHP Upload Script

We want an upload script that allows multiple file uploads where the user can select multiple files in a single window (much like freelancer.com or [login to view URL] upload). We also want to be able to set limitations on these uploads by size and file types. A progress indicator of each individual file is also needed. And we need to be able to add ways to handle these files with custom handlers that will defined later. The script should work on all recent browsers and render as a simple 1-file upload on older browsers.