Pony.fm/app/Commands/CommandBase.php

<?php

/**
 * Pony.fm - A community for pony fan music.
 * Copyright (C) 2015 Feld0
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

namespace App\Commands;

abstract class CommandBase
{
    private $_listeners = [];

    public function listen($listener)
    {
        $this->_listeners[] = $listener;
    }

    protected function notify($message, $progress)
    {
        foreach ($this->_listeners as $listener) {
            $listener($message, $progress);
        }
    }

    /**
     * @return bool
     */
    public function authorize()
    {
        return true;
    }

    /**
     * @return CommandResponse
     */
    abstract public function execute();
}