Help with PHP Code for Category Base Ads?

I am not PHP literate, and I want to see if the community could be kind enough to help write a php script? I use Google Ad Manager, and I need to add category specific ads to single posts. It will be nightmare if I have manually manage ads for each post/category. I assume the best approach would be to add php script to the page.php?

Can someone suggest an easily customizable php script for my site?
I think something like this would work:
‘If this post-category, then [insert Google Ad Manager javascript]; else, check for next category (repeat this call for however may categories I need);
if no categories match, then [insert Google Adsense javascript]
close php call’

I am open to other ideas if there is a better way to do this.

Thanks!
Chris