In my project I need to push some data from server to the client
like facebook
does, when some updates are performed in the clients profile
what you need is a comet/websocket approach, i do not know any PHP comet implementations/frameworks, yet there are several examples on the web when you search for it.
you can use node.js: http://nodejs.org/
You should take a look at the APE Project, which supports multiple variations that are as close to Push as you will get, like long-polling, XHRStreaming and WebSockets.
edit Doing this in just PHP is not the best choice, as it takes up a lot of resources to keep all those connections alive.