There is a somewhat similar tutorial here:
To simplify the whole thing you could bypass the ajax/jquery part of it. You could also bypass having a database and just append new messages to a text file.
So you'd have page1.php that would have the input form at the top and would iterate over the posts at the bottom. And then a submit.php which would take the input and append it to a file, with a timestamp. And then redirect you back to page1.php
If you haven't done much with PHP before you should take it slow, by looking up how to do each thing separately, like just submitting something first.