如何升级我的Java Web应用程序以使用PHP

I am new to Java web application development. I recently built a Java web application on my own and I have Tomcat server installed for the same. Recently I have learned Javascript, Jquery and then i learnt JSON and AJAX.

While I learn that with the help of JQuery and AJAX I can dynamically update my webpage.So i learnt some basics of PHP as well. But I don't understand where to place my PHP file !

I also read in the internet that apache server is better suited for executing PHP files. Now I have my java app all set with Tomcat server. I want to learn/make use of Jquery-AJAX-PHP functionality but stuck without knowing how to proceed further. Can anyone please advice me how to proceed with simple and detailed steps?

What all i want is to make a AJAX call from Java script to a PHP file and then echo a Hello.