It's easy enough to have php connect to an irc server, collect some text somewhere and what not.
There is no way to hide this fact though, anyone looking at the code could notice it and any admin looking at the outbound connections would also notice it. I suppose you could always try to make your code obscure looking so its hard to tell.
But in general it's considered bad practise to backdoor your clients, I can't think of any legit reason why it's required.
<Yoda> if someone says something i don't like, i ban him, ban whoever defends him, and then ban the witnesses...