Invoking External PHP to JavaScript

External sources for JavaScript and an Ajax based application used to be ill advised to developers for security purposes. However, because of the advancement of JavaScript techniques and more security measures implemented in coding, invoking a source outside the client side is already tolerable. Invoking external functions could be possible as long as they come with .js file or the specified data format of the application such as CSS or JSON. But if the developer wants to push further for more data and interaction, they could even invoke PHP as part of their application. This might seem impossible at first but because of the increased functionality of JavaScript, developers can no