Simple Google Analytics WordPress plugin

google-analytics-plugin.php

<?php

/**
 *
 * Simple Google Analytics WordPress plugin
 *
 * @link              https://www.fernan.com.es/
 * @since             1.0.0
 *
 * Plugin Name:       Fernan Google Analytics
 * Plugin URI:        https://www.fernan.com.es/
 * Description:       Plugin para añadir  Google Analytics en el sitio web.
 * Version:           1.0.0
 * Author:            Fernan Díez
 * Author URI:        https://www.fernan.com.es/
 * License:           GPL-2.0+
 * License URI:       http://www.gnu.org/licenses/gpl-2.0.txt
 * Text Domain:       google-analytics-plugin
 * Domain Path:       /languages
 */

 // Adds Google Analytics code to the header
 function fernan_analytics_code() { ?>

  <script async src="https://www.googletagmanager.com/gtag/js?id=UA-XXXXXXXX-1"></script>
  <script>
    window.dataLayer = window.dataLayer || [];
    function gtag(){dataLayer.push(arguments);}
    gtag('js', new Date());
  
    gtag('config', 'UA-XXXXXXXX-1');
  </script>

 <?php }
 add_action('wp_head', 'fernan_analytics_code');

Important reminder!

Replace in both places:
"UA-XXXXXXXX-1"
with your tracking code:
"Your Google Analytics own tracking code"