The new release of the Silverlight Multi File Uploader includes a PHP version.
You're now able to host the Multi File Uploader on a PHP server (for example Apache). Silverlight doesn't requiere .Net on the server. It uses a small .Net Framework on the client.
But the files need to be processed on the server. Until now the project included only a .Net implementation to receive the files. In the new release, there's also a PHP implementation available.
Configure the Silverlight Multi File Uploader to use the HttpUploader and specify the name of the PHP script.
<param name="initParams" value="HttpUploader=true,UploadHandlerName=PHPUpload.php,DefaultColor=Green" />
See the included PHP testpage (PHP_SilverlightMultiFileUploadTestPage.html) for example usage.
Download the Silverlight Multi File Uploader at CodePlex
You can see the control in action here.