First off, only one line of code is mIRC, I'm guessing you added that in, and its

Code:
on *:TEXT:@wall*:#:{


Everything else is PHP. You can Google random lines of code curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); if you want, and you will find PHP references.

If you have seen others run it, that's because they are running it on a PHP server/machine or whatever they are called. NOT mIRC.