You want a content management system. First you need somewhere to store the form data, like a db or a textfile. The form, say diary_entry.php, will display the form elements and handle the data once you hit submit. ie: it will store it into the db or textfile. Only you see this page.
When someone goes to your index.php, you have it set up so that it grabs the info from the db or textfile and displays it however you want, using stylesheets or whatever. PHP is the perfect solution for this. It's easier with a db but if you don't have one you can still use a textfile.
It's a little more comlpicated showing you exactly how in this small space, but if you want an example I can probably send you one.
Dave
