From my perspective, the concept of PHP and MySQL is very easy. The biggest problem you are going to have, will be with installation. For the learning purpouse I would encourage you to install PHP, MySQL, and Apache separately, one by one. There is a good tutorial, although a litte outdated over at the webmonkey. I do have my own tutorial as well, if you want it, PM me I can search and send it to you (my tutorial is for windows though). Also make sure that you are going to install and configure phpmyadmin, which is nothing more than a GUI interface to MySQL. This little program is very handy, although once again it takes a while to configure. Overall, PHP seems is a very forgiving scripting language. It is very easy to learn, especially if you had some previous programming experience with Java or C++....
You will be just fine!