Allowing others to post comments via PHP

[EJ12N]

I need to add this.

I am limiting the amount of characters someone can input, however; I'm not sure whatelse to do. How can I make sure they're on the apge for, like 20 seconds before posting? Or do you have other recommendations?

yes either save in a file their IP,TIME or do it by mysql

then in ur script check if that IP has posted any msges in last X minutes u want...additionally u can register session variable or put a cookie
something like $_SESSION['last_comment'] = time();
then in ur script check for that...I hope you get the idea