A very simple event system for PHP Projects

EventSystem.php

<?php

/**
 * A class to implement a simple event system in any PHP project.
 *
 * @author Nick Andriopoulos <[email protected]>
 * @license https://www.apache.org/licenses/LICENSE-2.0
 */

/**
 * A simple event system for any PHP Project
 */
class EventSystem
{
  static $eventmap;

  /**
   * Register an event before it becoming available for use
   *
   * @param string $eventname
   */
  public static function registerEvent($eventname) {
    if(!isset(self::$eventmap[$eventname])) {
      self::$eventmap[$eventname] = array();
    }
  }

  /**
   * Subscribe to a defined event.
   *
   * @param string $eventname
   * @param string $callback
   * @param int    $weight
   */
  public static function subscribeToEvent($eventname, $callback, $weight=0) {
    if(!self::validEvent($eventname)) { return false; }
    self::$eventmap[$eventname][$weight][] = $callback;
  }

  /**
   * Trigger an event, and call all subscribers, giving an array of params.
   *
   * @param string $eventname
   * @param array  $params
   */
  public static function triggerEvent($eventname, $params) {
    if(!self::validEvent($eventname)) { return false; }
    foreach(self::$eventmap[$eventname] as $key => $weight) {
      foreach($weight as $callback) {
        call_user_func_array($callback, $params);
      }
    }
  }

  /**
   * Check that an event is valid before interacting with it.
   *
   * @internal
   *
   * @param string $eventname
   */
  public static function validEvent($eventname) {
    if(!isset(self::$eventmap[$eventname]) || !is_array(self::$eventmap[$eventname])) { return false; }
    return true;
  }
}

/* Simple Example */

/* Delete this line to enable testprint!

// On website boot, create your event....
# include('EventSystem.php'); // If the class were in a different file, include it.
EventSystem::registerEvent('prelogin');

// Module 1 needs to do stuff then ( anywhere in the project )
EventSystem::subscribeToEvent('prelogin', 'myprelogin');

// Module 2 too!  ( anywhere in the project )
EventSystem::subscribeToEvent('prelogin', 'anotherprelogin');

// The actual website will then trigger the event when it's time,
//  with the params expected by the implementors
EventSystem::triggerEvent('prelogin', array('nick', 'asdf'));


// Sample module 1 function:
function myprelogin($username, $password) {
  print 'My Username is: '.$username."\n";
  print 'My Password is: '.$password."\n";
}

// Sample module 2 function:
function anotherprelogin($username, $password) {
  print 'Just wanted to join in the fun!';
}