What version of PHP are you running?

Cool - thanks. I must have been sort of nuts when I replied. I see the line now. I'll see if I can remove that dependency.

There is no need for SimpleXML. Please take a look at the source to see for yourself.

Modified and updated the script. This version correctly handles @replies (I think - tested only by preventing them), correctly allows RTs to be posted, does not cut off retweets when they are posted by API (which results in them being truncated).

I've modified much of the code for reading clarity and added comments.

http://pastebin.com/h0hDfeXX

Your code checks for '@' is in the string, rather than if it is the first character. I'd suggest switching over to strncmp to correctly allow for tweets with '@' in it.