Limiting Parallel/Simultaneous Downloads - How to know if download was cancelled?

Question

I have a simple file upload service, written out in PHP, which also includes a script that controls download speeds by sending limited-sized packets when a user requests a d

Answer 1

You will want to check out the following functions: connection_status(), connection_aborted() and ignore_user_abort() (see the connection handling section of the PHP manual for more info).

Although I can't guarantee the reliability (it's been a while since I've played around with it), with the right combination you should be able to accomplish what you want. There are a few caveats when working with these though, the big one being that if something goes wrong you could end up with stranded PHP scripts running on the server requiring you to kill Apache to stop them.

The following should give you a good idea of how to do it (adapted from the PHP code examples and a couple of the comments):

Obviously for how you would be using it the data being sent would simply be the download data chunk (just make sure you flush the buffer properly to ensure the data is actually sent). As far as I'm aware, there is no way of making a distinction between pausing and aborting/stopping. Pause/resume functionality (and multi-part downloading - i.e. how download managers accelerate downloads) relies on the "Range" header, basically requesting byte x to byte y of the file. So if you want to allow resumable downloads you'll have to deal with that too.