FRONTEND_MVC/modules/control/Control.php

<?php
namespace control;

if(!function_exists('print_a')){
	function print_a( $a ){
		echo "<pre>";
			print_r( $a );
		echo "</pre>";
	}
}

use yii\base\Module;

class Control extends Module
{
    public $layout = "@control/views/layouts/main.php";
}