No, your script does not take control until the upload has completed. The APC stuff mentioned in a comment above is limited to PHP writing out upload status to a file elsewhere on the system, which can then be read by another script to send out as progress information.
But while an upload is going, you cannot do anything with that connection until the upload completes or is aborted.
PHP is also badly suited for very large uploads - consider what happens if your link were to hiccup 10bytes from the end of that very long/large upload. Since PHP is not in control of the upload, there's no way to resume. FTP/SFTP are better suited for such things, especially since they won't delete an aborted upload.