シンプルなデリゲートの実装

C#ライクなデリゲートの実装

<?php

class Delegate
{
    /** @var callable[] */
    protected $callbacks = [];

    /**
     * Add callback function
     * @param callable $callback
     * @return $this
     */
    public function add(callable $callback)
    {
        $this->callbacks[] = $callback;
        return $this;
    }

    /**
     * Remove callback function
     * @param callable $callback
     * @return $this
     */
    public function remove(callable $callback)
    {
        foreach ( $this->callbacks as $key => $_callback )
        {
            if ( $callback == $_callback )
            {
                unset($this->callbacks[$key]);
                return $this;
            }
        }
        return $this;
    }

    /**
     * Invoke callback functions
     * @return mixed
     */
    public function __invoke()
    {
        $result = null;

        foreach ( $this->callbacks as $callback )
        {
            $result = call_user_func_array($callback, func_get_args());
        }

        return $result;
    }
}

$callback = function($name) {
    echo "Hello $name", PHP_EOL;
};

$delegate = new Delegate();
$delegate
    ->add($callback)
    ->add($callback)
    ->remove($callback);

$delegate("World");