title: How does push email/chat work? Can it be implemented easily for small websites?
body: <p>I am trying to understand how push services work. I believe push notifications are where the server 'pushes' a new item to the client, but I don't know how that works in practice.</p>
  
  <p>For example, how does a phone "know" that it has a new email to pick up if it doesn't manually check the server for a new message?</p>
  
  <p>Also, how can this be implemented for a chat program or notification system for a small website? Are there php classes out there, etc..?</p>