[feldon23]

Another point I must raise is that there are very real limits on the number of users this script can handle.

Because the list of users is being sent through a URL, you may slam into URL length problems if you have 60+ users in your chatroom.

I am paraphrasing here...
Although the RFC referring to URLs does not indicate a fixed length, Internet Explorer cannot handle more than 2083 characters in a URL and some proxy servers limit the # of characters to 255.

I am 99% sure that the PHP script will simply truncate a lengthy URL and provide an incomplete nick list, even if a nick boundary falls on a + character. I am not sure, however, what mIRC will do. It might fail to send any part of the URL.

I suppose some kind of buffering system could be created with "action=write" followed by a series of "action=append". Heaven help us if the appends arrive out of sequence.

Still, I'm pretty darn happy with how this hack is working.

VeloCD, you can imagine that adding the topic would be a huge stumbling block for URL length. A topic like this (from "A Fish Called Wanda"):
"It's k-k-k-Ken and he's c-c-c-coming to k-k-k-kill me!"

would expand to something like:
%26It's%20k-k-k-Ken%20and%20he%25s%20c-c-c-coming%20to%20k-k-k-kill%20me!%26

Again, I can forsee this being handled with "action=topic&topic=...", etc.