PHP实现事件机制实例分析

<?php
/**
* 事件
*
* @author xiezhenye <xiezhenye@gmail.com>
*/
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], $args[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 be called in holder'));
}
foreach ($this->callbacks as $callback) {
$args = func_get_args();
call_user_func_array($callback, $args);
}
}
}