I would suggest that you base this on a database instead (eg. sqlite), and then check that every post is displayed on the wall, because with the current script, two people could post something almost at the same time, and then one of the posts won't be displayed.
But maybe that is wanted, with the benefit of having some updated posts that could comment what was happening on the set, instead of having a 10 minute queue for getting a post shown.
If you want this I could try to put something together...
Edit: Oh btw, it would also be easy to add a validation system to the above solution, so a person has to approve each post before they get into the queue, in order to limit spam and ads.
Edit 2: I just saw the 3x11 episode, and if you want people to post ascii art on the wall, you probably need to enclose the text in <pre> tags, or at least make newlines (\n) into HTML newlines (<br />).