// main plugin file, frequentVisitorCoupons.php
require 'vendor/autoload.php';

// the first argument points to this file because I think
// autoload automatically loads the Utilities class here
register_activation_hook(plugin_dir_url(__FILE__) . 'frequentVisitorCoupons.php',
 'Utilities::createTablesIfNotExists');


// classes/utilities.php
<?php
class Utilities {
  public static function createTablesIfNotExists() {
    global $wpdb;

    $createCouponTableQuery = "CREATE TABLE IF NOT EXISTS {$wpdb->prefix}frequentVisitorCoupons_coupons (
    couponId MEDIUMINT NOT NULL AUTO_INCREMENT UNIQUE,
    PRIMARY KEY  (couponId),
    totalHits MEDIUMINT NOT NULL,
    isText BOOLEAN NOT NULL,
    imageUrl TEXT(1000)
    )";

    <2 more table create queries removed>

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

    var_dump($wpdb->queries);
    echo <<<'EOD'
    =====$wpdb->queries=====
EOD;
  }
}