观察者模式

observer-example.php

<?php
/*
观察者模式的核心在于允许你的应用程序注册一个回调，当某个特定的事件发生时便会触发它。
*/
class Event {
  static protected $callbacks = array();
  
  static public function registerCallback($eventName, $callback)
  {
    if (!is_callable($callback)) {
      throw new Exception("Invalid callback!");
    }
    
    $eventName = strtolower($eventName);
    
    self::$callbacks[$eventName][] = $callback;
  }
  
  static public function trigger($eventName, $data)
  {
    $eventName = strtolower($eventName);
    
    if (isset(self::$callback[$eventName])) {
      foreach(self::$callbacks[$eventName] as $callback) {
        // The callback is either a closure, or an object that defines __invoke()
        $callback($data);
      }
    }
  }
}

class MyDataRecord {
  public function save()
  {
    // Actually save data here
    
    // Trigger the save event
    Event::trigger('save', array("Hello", "World"));
  }
}

class LogCallback {
  public function __invoke($data)
  {
    echo "Log Data" . PHP_EOL;
    var_dump($data);
  }
}

Event::registerCallback('save', new LogCallback());
Event::registerCallbacl('save', function ($data) {
  echo "Clear Cache" . PHP_EOL;
  var_dump($data);
});

$data = new MyDataRecord();
$data->save();    // 'save' Event is triggered here