My PECL uploadprogress bar appears, but why doesn't it show any progress?
Have a look at the (very old) issue # 633862. Even though it's an old issue, it includes quite a few comments that may help you to find "the clue". E.g. that it it doesn't seem to work for the more "exotic" server configurations.

Comment # 41 states this:


  Apparently secure servers also have an issue with it https:// won't work with this.


Comment # 43 in that issue also suggest the (sandbox for now)  upload_progress module, here is what that comment includes:


  I have created a little module that uses client-side JavaScript instead of server-side code to display the progress. This will finally bring upload progress to more "exotic" server configurations.