title: Extending or adding action to a function
body: <p>Is it possible to extend a php function ?</p>
  
  <p>if no how does WordPress <code>add_action()</code> works ? </p>
  
  <p>can you guys suggest me <code>add_action</code> like function for non wordpress system ?</p>
  
  <p>Thanks for help</p>