How to write HTML/PHP code for posting comments from customers?

I would like to know what is the HTML/PHP code to allow a person to post a comment on a website?
I am going to design a website with this ability the customers can post comments?

You want a guestbook, and it is quite easy to achieve.

http://www.phpeasystep.com/phptu/15.html

There’s also http://www.dreambook.com if you don’t want to get into the nitty-gritty of it.

You can also search out shoutboxes, which are quite popular on the Web.