Depending on what exactly you want to do with the images, there are a number of php functions you need to be aware of. Go here and look at them:
http://uk2.php.net/manual/en/functio...opyresized.php
The page name in the url is just to get you to the right area. You will see all the graphic functions listed down the left-hand side of the page.

As far as database storage is concerned, I'm assuming you are using mysql so you will need to be defining your fields using a 'blob' field to store your image. It is also worth storing things like the file type, mime type, etc., as this will make future manipulation easier.