title: How to implement a push notification system on a website in PHP?
body: <p>I would like to ask if someone knows how can I notify a user that looks at a page of my website with a push notification (i.e. make my server notify the user that there's something to him). </p>
  
  <p>I understand the polling mechanism (I can implement it through a simple loop with a setInterval() in Javascript and pass a callback that makes an async XMLHttpRequest or a getJSON), but what about the push mechanism?</p>
  
  <p>I guess I need to make a sort of a call with the server that should tell the client that it has something for him??? Assuming that my website is in PHP, is there a way to make it?</p>
  
  <p>Thanks for the attention!</p>