php code to grab an IP

there are a couple of users who keep posting stupid stuff in my site and i just have to keep deleting the posts. is there any way i can detect their ip so i can deny it from the control panel?

You can get the IP with 'REMOTE_ADDR', take a look at the Predefined Variables
But, that's an unreliable way to do it, as their IP isn't going to be the same each time. You should have something set up to manage your users, where it allows you not allow those certian users to post.

Good luck;