PHP Events

<?php

class Event {
    static protected $_events = array();

    static public function attach ($event, $method) {
        if(!is_string($event))
            throw new \InvalidArgumentException('$event should be a string.');
        if(!is_callable($method))
            throw new \InvalidArgumentException('$method is not callable.');

        $class = get_called_class();
        if(!isset(self::$_events[$class]))
            self::$_events[$class] = array();
        if(!isset(self::$_events[$class][$event]))
            self::$_events[$class][$event] = array();

        self::$_events[$class][$event][] = $method;
    }

    static public function trigger ($event, $arguments = array()) {
        $class = get_called_class();
        if(!isset(self::$_events[$class]) || !isset(self::$_events[$class][$event]))
            return;
        foreach(self::$_events[$class][$event] as $method)
            call_user_func_array($method, $arguments);
    }
}

// the extending class
class Page extends Event {
    public function render ($context) {
        self::trigger('before-render', array(&$context));
        $result = print_r($context, true);
        self::trigger('after-render', array($result));

        return $result;
    }
}

// in your setup file, plugins, etc.
Page::attach('before-render', function ($context) {
    $context['active'] = true;
});

// rendering something:
$page = new Page();
echo $page->render(array('name' => 'Jacob'));
// Array
// (
//  [name] => Jacob
//  [active] => 1
// )