Blaears now listens on /blaupload for POSTs containing 'url' and 'channel', and will post those URLs to that channel.
I've added a config value $posturl for the URL to post to - if this is not set then nothing will be done.
If it is set, then it will send a POST containing the uploaded file URL and the channel set in $postchannel in the config.
I'm not sure on best practice for global variables in PHP. I passed them in as function arguments, but we could also use 'global $posturl, $postchannel' instead.