This is a different variation of the virtual pet theme.
This is pretty straight forward, but an excellent project to learn PHP and database development - mySQL would be my choice of databases because there are lots of howto articles to help you.
I suggest that you start with PHP sites such as the following and begin reviewing articles and code:
http://www.findingfacts.com/L3/L3_2_29_46.php
You probably won't find the exact code segment that you need, but eventually you will cobble together enough code snipits to do the job. On the way you will have learned to use PHP because it's a very easy language to learn. Next I would look at pages such as this on MySQL and learn databases:
http://www.findingfacts.com/L3/L3_54_55_59.php