使用Ajax请求执行PHP文件

Still grasping Ajax, so I beg your patience. I am trying to run a php file from within javascript using an ajax call with the help of jQuery. I do not need to GET / POST any data, I just intent the PHP code to be executed and the message 'hello world' logged to the console (I intend to use this in a button with an onclick() function). The only thing that gets logged is the "success" message. I want the PHP code to execute without leaving the current page, but I think I may be missing how AJAX works. Or perhaps there is a better way to accomplish this. Thanks for helping out.Still grasping Ajax, so I beg your patience. I