Php和JQuery——如何对访问站点页面的计算机可见的页面进行更改

I have a simple social networking site wherein there's a post function that saves the post and displays it as a new div within a list at the top of the unordered list, basically, it acts like a timeline. The problem is that, the current code that I have only works for the current PC that is viewing the page. What is the proper way of using JQuery .ajax() for handling this scenario ? For example, there are two PC's, PC 1 and PC 2. PC 1 posted something and they saw it display on the timeline. Now, PC 2 can't see that the timeline is updated. I have a simple social networking site wherein