How do I find out which addresses are the inputs of a given transaction, given its transaction ID? I know there is a way, as satoshidice.com uses this. I would like to do this with own software and not rely on some third party provider, which could easily kill their service.
Basically I'm creating a PHP project, where I need to find out when a new transaction arrives and which address sent it. So I need a way to get a notification or start a PHP script (called with needed variables [txid, sender address, receiving address, value]) when a new transaction arrives.