WHM PHP Plugin Development

Hey Guys, Please ignore my ignorance, I know there are hordes of documents and guides for exactly what I am asking. I have been working through just about all of them with no success. So I wanted to ask in another way... I want to create a WHM plugin, This plugin will be coded in PHP (most guides are for cgi so that's where I kinda lose it). Has anybody made a step by step guide for a php plugin development? Locations for the files and so forth? Or does someone have a simple sample plugin that I can use to determine what I need to make happen? Thanks in advance guys :).