WordPress style hooks in a class.

Hooks.php

<?php
/**
 * Implementation of WordPress style hooks.
 *
 * @author      Christopher Davis <chris [AT] classicalguitar.org>
 * @copyright   Christopher Davis 2012
 * @license     MIT
 */

class Hooks
{
    protected $hooks = array();

    protected $done = array();

    public function act($hook)
    {
        return $this->perform($hook, array_slice(func_get_args(), 1));
    }

    public function filter($hook)
    {
        return $this->perform($hook, array_slice(func_get_args(), 1));
    }

    public function add_action($hook, $callable, $prio=10)
    {
        return $this->add($hook, $callable, $prio);
    }

    public function remove_action($hook, $callable, $prio=10)
    {
        return $this->remove($hook, $callable, $prio);
    }

    public function add_filter($hook, $callable, $prio=10)
    {
        return $this->add($hook, $callable, $prio);
    }

    public function remove_filter($hook, $callable, $prio=10)
    {
        return $this->remove($hook, $callable, $prio);
    }

    public function has_action($hook, $callable, $prio=10)
    {
        return $this->has_hook($hook, $callable, $prio);
    }

    public function has_filter($hook, $callable, $prio=10)
    {
        return $this->has_hook($hook, $callable, $prio);
    }

    public function did_filter($hook)
    {
        return $this->did_hook($hook);
    }

    public function did_action($hook)
    {
        return $this->did_hook($hook);
    }

    /********** Internals **********/

    protected function build_id($func)
    {
        if(is_scalar($func))
            return $func;

        if(is_object($func))
            $func = array($func, ''); // closures are objects

        $id = is_object($func[0]) ? spl_object_hash($func[0]) : $func[0];

        $id .= !empty($func[1]) ? $func[1] : '';

        return $id;
    }

    protected function perform($hook, $args)
    {
        if(isset($args[0]))
            $value = $args[0];
        else
            $value = null;

        if(!isset($this->hooks[$hook]))
            return $value; // bail, nothing set for this hook.

        ksort($this->hooks[$hook], SORT_NUMERIC);

        reset($this->hooks[$hook]);

        do {
            foreach(current($this->hooks[$hook]) as $idx => $func)
            {
                if(!is_callable($func))
                    continue; // maybe this shouldn't get checked?

                $args[0] = $value;
                $value = call_user_func_array($func, $args);
            }
        } while(next($this->hooks[$hook]) !== false);

        $this->done[$hook] = true;

        return $value;
    }

    protected function add($hook, $func, $prio)
    {
        $prio = intval($prio);

        !isset($this->hooks[$hook]) && $this->hooks[$hook] = array();

        !isset($this->hooks[$hook][$prio]) && $this->hooks[$hook][$prio] = array();

        $this->hooks[$hook][$prio][$this->build_id($func)] = $func;
    }

    protected function remove($hook, $func, $prio)
    {
        if($this->has_hook($hook, $func, $prio))
        {
            unset($this->hooks[$hook][$prio][$this->build_id($func)]);
            return true;
        }

        return false;
    }

    protected function has_hook($hook, $func, $prio)
    {
        return isset($this->hooks[$hook][intval($prio)][$this->build_id($func)]);
    }

    protected function did_hook($hook)
    {
        return isset($this->done[$hook]);
    }
}