How to implement event mechanism in PHP _php skills

The examples in this article describe how PHP implements the event mechanism. Share to everyone for your reference. as follows:

<?php/** * Event/class Event {Private $callbacks = array ();
 Private $holder;
  function __construct () {$BT = Debug_backtrace ();
   if (count ($BT) < 2) {$this->holder = null;
  Return
 } $this->holder = & $BT [1][' object '];
  function Attach () {$args = Func_get_args ();
     Switch (count ($args)) {Case 1:if (is_callable ($args [0])) {$this->callbacks[]= $args [0];
    Return
   } break; Case 2:if (is_object ($args [0]) && is_string ($args [1])) {$this->callbacks[]= array (& $args [0], $ar
    GS[1]);
   } return;
  Default:return;
  }} function Notify () {$BT = Debug_backtrace ();
    if ($this->holder && ((count ($BT) >= 2 && $BT [Count ($BT)-1][' object ']!== $this->holder) || (Count ($BT) < 2)))
  {Throw (New Exception (' Notify can only is called in Holder '));
   foreach ($this->callbacks as $callback) {$args = Func_get_args (); Call_user_func_array ($callbacK, $args);

 }
 }
}

I hope this article will help you with your PHP programming.