利用回掉函数增强可扩展性

<?php 

class Listener
{	
	public static function handle()
	{
		static $count = 0;
		return function(Event $event) use ($count) {
			echo "eventName=" . $event->name . " and count=" . $count . "-----in listener function<br>";
			$count += 1;
		};
	}

}


abstract class Event
{
	public $name;
	public $callback = [];

	public function __construct($name)
	{
		$this->name = $name;
	}
	
	public function registerListener(Closure $callback)
	{
		if(! is_callable($callback)) {
			throw new Exception("callback is not callable", 1);
		}
		$this->callback[] = $callback;
	}

	public function setUp()
	{
		static::handle();
		foreach ($this->callback as $callback) {
			call_user_func($callback, $this);
		}
	}

	abstract public function handle();
}

class SaleEvent extends Event
{
	
	public function handle()
	{
		echo "handle function in SaleEvent<br>";
	}
}
function init()
{
	return $kernel = [
		'SaleEvent' => [
			'Listener',
		]
	];
}
function event(Event $event)
{
	$relations = init();
	$className = get_class($event);
	$listeners = $relations[$className];
	foreach ($listeners as $value) {
		$event->registerListener($value::handle());
	}
	return $event->setUp();
}

event(new SaleEvent('saled'));

　　

这样以后如果有其他监听该事件的listener，直接添加进kernel数组即可。