I'd definitely be up for this... We have an already published app which used to have a leaderboard, but we had to remove it due to lack of someone hosting the scoreboard for us (I have 0 knowledge of PHP sadly). I still have all the code in place and would be happy to be your guinea pig to try this out if you'd like...
The way we did it before was with the HTTP request, like this (for sending a score);
SendHttpRequestASync(ScoreConnection, "/boxshot/update.php?PName=" + SendName + "&PScore=" + Str(SendScore) + "&Verify=[Password]")
And then for retrieving the scoreboard, we simply got passed back a huge string with all the names and scores. I then parsed this in AGK... If you are interested (as I am) then send me an email and we can discuss more in detail