slack-commands.php

class autoloader {

    public static $loader;

    public static function init()
    {
        if (self::$loader == NULL)
            self::$loader = new self();

        return self::$loader;
    }

    public function __construct()
    {
        spl_autoload_register( array($this,'commands') );
    }

    public function commands( $class ) {
		set_include_path( plugin_dir_path( __FILE__ ).'commands/');
        spl_autoload_extensions('.command.php');
        spl_autoload($class);
	}

}

//call
autoloader::init();