Hi,
First, maybe it would be good to install PHP (and, of course, Apache and MySQL) on your computer. Here is a tut : http://www.patheticcockroach.com/mpam4/index.php?p=32
Then, to get started with PHP, I think the W3Schools tut is nice, here : http://www.w3schools.com/php/default.asp
Then, read scripts along with the PHP reference to search for the functions you don't know.