PHP with Javascript tutorials?

Hi there everyone, I've been looking on Google for PHP Javascript tutorials but I can't find any. I'm new to Javascript but can use PHP for what I need. I was hoping someone would know of a tutorial that would show how to use PHP to get 2-3 datasets which javascript can then use in forms. For example, say I have 3 pulldown boxes, one would have countries - such as UK, USA etc .. If you selected the UK it would bring up countries in the UK, and if you select a country the third pulldown would show the cities in that country (This is just an example to hopefully explain what I need) but I don't want the page to refresh everytime I select an option which it does if you just use PHP. Any help would be EXTREMELY greatly received :-) Regards Chris