However, you can also do uploads with Flash. You can show the progress bar purely client-side because Flash provides upload progress information.
I see. The video is stored in a database, and you want to stream it from there. Hmmm. A media player needs a URL to connect to, which the database doesn't supply. You could presumably write a PHP script to read it from the database and use the script's URL as the source for the player. But guess what? Database engines aren't designed for streaming media. There's no SQL query that will dole out the contents of a field at a measured pace. You'll have to transfer the file to the filesystem before streaming it. Since it will presumably be viewed by many people, you may as well store it on the filesystem in the first place. Otherwise your database server is going to get really slow.
World Wide Weird, if that would the case, how am I going to secretly download the file from the filesystem? I mean, when the user click on the [Play this Video] link on the page, I don't like to show the download dialog box on the screen.
I don't understand the question. Do you want to retrieve the file from the database and store it on the filesystem as a regular file? Use a SELECT statement to get it into a variable, then use file_put_contents() to write it to a new file.