I'd suggest starting with the manual at www.php.net and reading up on form interactions and database queries to write it yourself, then you can ask us questions when you encounter problems.
Or, you could look around www.hotscripts.com or similar sites for a pre-made script.
OR! You could Google "php developers for hire" and pay someone to do the work for you.
We're here to help, not to just flat-out do the work for you. 😉