Custom multisite plugin not creating tables

Hi

I’m trying to write a custom plugin for a multisite installation.
I’m using Shiba’s method from here

It’s not creating the tables and I’m getting this message on activation:

The plugin generated 2412 characters of unexpected output during activation.

Here’s my complete plugin code:

<?php
/*
Plugin Name: Messages
Plugin URI: https://www.whatever.com
Description: Messages Plugin
Version: 0.1
Author: Whoever
*/

class msgLoader {

	function msgLoader() {

		register_activation_hook( __FILE__, 'multisiteActivate' );
	}

	function create_inbox_table($table_name) {
		global $wpdb;

			$sql = "CREATE TABLE IF NOT EXISTS '$table_name' (
			  	id bigint(20) NOT NULL AUTO_INCREMENT,
				from varchar(255) NOT NULL,
			  	message varchar(255) DEFAULT NULL,
			  	UNIQUE KEY id (id)
			);";

		require_once(ABSPATH . 'wp-admin/includes/upgrade.php');
		dbDelta($sql);
	}

	function multisiteActivate() {
		global $wpdb;

		if (function_exists('is_multisite') && is_multisite()) {
			// check if it is a network activation - if so, run the activation function for each blog id
			if (isset($_GET['networkwide']) && ($_GET['networkwide'] == 1)) {
		                $old_blog = $wpdb->blogid;
				// Get all blog ids
				$blogids = $wpdb->get_col($wpdb->prepare("SELECT blog_id FROM $wpdb->blogs"));
				foreach ($blogids as $blog_id) {
					switch_to_blog($blog_id);
					$this->activate();
				}
				switch_to_blog($old_blog);
				return;
			}
		}
		$this->activate();
	}

	function activate() {

		global $wpdb;

	        $table_name = $wpdb->prefix . 'inbox';
			if ($wpdb->get_var( "SHOW TABLES LIKE '$table_name'") != $table_name) {
				$this->create_inbox_table($table_name);
	        }
	}
}
global $msg;
$msg = new msgLoader();
?>

Any help would be greatly appreciated.

Thanks in advance

Dyrk